Wolfman and Perez had many practical tasks to accomplish with Crisis, inarguably more in the way of substantial change than any mega-event before or after. First, as discussed before, the series was conceived as a celebration for fifty years of publishing on the part of DC Comics nee National. It's expected that any anniversary celebrated in the pages of a comic will be something resembling an exhaustive - or at least capacious - summation of the preceding interval. (DC was especially good at these kinds of events in the 80s - for example, see here, here and here.) The fact that the creative team behind Crisis actually took a fair stab at encapsulating the previous fifty fifty years - not merely of a single character's run but of the sum total of thousands of comics in multiple genres - is simply astounding.
But there was something more pressing and more melancholy at hand for a large percentage of the characters and genres utilized at various points throughout the series. Although I've never heard it discussed as such by anyone involved (perhaps it's come up in Alter Ego or one of those related interview publications at come point), but it can't have escaped the notice of those responsible for creating the book that many of these characters were probably never going to be used again. Although, to be fair, a large amount of seemingly superfluous concepts that were obviated by the Crisis have survived as perpetual cameo fodder - with even the occasional star turn from a seemingly forgotten property in the pages of an obscure book or prestige-format revival - it was not so easy back in 1985 to imagine auspicious futures for the likes of Cave Carson, Tomahawk, and the Balloon Buster. Giving two panels or a half-page to forgotten properties such as the gunslinger Nighthawk or the Prince Gavyn Starman was, considering the circumstances, incredibly generous. More of these characters have survived in one form or another than anyone could reasonably have expected at the time, but flipping through Crisis and its companion Who's Who still reveals many faces that have since faded into complete obscurity - Knights of the Galaxy and Firehair, we hardly knew ye.*
But the changes underfoot were not entirely backwards-looking - for every character being trotted out for their figurative last hurrah, there was another character waiting in the wings. Wolfman & Perez created a handful of characters out of whole cloth, which should not go unmentioned. It's probably reasonable to expect that the Monitor, Harbinger and Pariah were never expected to have a significant shelf life after the series ended (well, Wolfman might have thought differently, but those guys were pretty much created for the express purpose of being plot devices in one story), but even on top of those there was Lady Quark (who did stick around for a while, in L.E.G.I.O.N., a believe), Dr. Light II (an interesting character who still appears occasionally), WIldcat II (Yolanda Montez, who is completely gone), and of course, the Wally West Flash, perhaps the single most successful launch to come directly out of the series short of Byrne's Superman. The creators seem to have been uniquely sensitive to accusations of bloody-minded destructiveness, and did their best to open a few doors in return for the many doors closed over the course of the series.
The biggest opened doors, however, were actually entirely new - or, "new" in scare-quotes - families of characters, long held by DC but only then actually incorporated into the DC Universe proper. In some cases, such as the Fawcett characters (Captain Marvel and his family), as well as the Quality heroes (Uncle Sam & the Freedom Fighters), the characters were not entirely unfamiliar to DC readers, having appeared alongside their Earth-1 and Earth-2 counterparts at various points since having been purchased by the company.** The Charlton heroes, on the other hand, had never appeared in a DC Comic - hadn't even appeared regularly since 1968, I want to say - and their introduction consequently needed to be sold as something of a big deal (this is commented on in a sideways fashion at various points throughout the series, with the Charlton heroes being completely unfamiliar with the mores of inter-dimensional super-hero team-ups). Wolfman and Perez not only had to reintroduce all of these characters - who, if having appeared at all, had only appeared sporadically in the previous decades - but they had to make a case for them as being important in the context of an already very large superhero universe. This is one instance where the unified post-Crisis Earth enabled a number of stories to be told that would otherwise have been a far more difficult sell: a Charlton revival explicitly labeled as occurring on Earth-C (or whichever, I forget which earth it officially was) would probably not have had the appeal of a Charlton revival that saw the Blue Beetle and Captain Atom as keystone members of a revived Justice League. Of course, it bears mentioning that it's still a point of debate as to whether or not Captain Marvel gained anything by being completely integrated into the DCU since the tone of his best stories differed considerably from that of the post-1985 mainline DC Universe publishing slate. But if the only alternative to wholesale incorporation was the near-total obscurity of being "out of continuity," it's probably better that the character retained some prominence as a participating member of a larger superhero continuity.***
The final accomplishment of Crisis is the most obvious one, and in hindsight the most problematic: the establishment of the new post-Crisis single-Earth status quo. While on paper the post-Crisis integration may have seemed like the most logical solution to proliferating complexity, in actuality the benefits of the streamlined New Earth were severely mitigated by the company's absolute refusal to disengage from the practice of constantly updating and "fixing" lapsed continuity. Post-Crisis, the smartest thing they could have done would have been simply to stop caring so much about consistency: with a working model New Earth and streamlined continuity, they should have declared Crisis #12 (or, more likely, Man of Steel #1) ground zero and gone forward without so much as a backwards glance, making it up as they went and not worrying so much about the particulars. But of course it didn't work like that. There were problems immediately out of the gate: Roy Thomas and Paul Levitz, to name two prominent offenders, did not easily incorporate their distinctive and disparate fiefdoms - Earth 2 and the 30th Century, respectively - into the New Earth continuity, and therefore proceeded to pick at the scabs of bruised continuity in such a way that, for many characters and settings, the transplant never entirely took. Hawkman was problematic as well - but again, instead of simply just shrugging and going forward, they insisted on making a big deal of the problem, and thereby drawing more attention to what should have been merely a glitch.
The problem with Crisis - or, at least, one significant problem - was that, in concocting such an elaborate and all-encompassing continuity patch, fans and creators alike came to expect that, going forward, like discrepancies and inconsistencies would be rigorously and mercilessly hounded to extinction. The point of Crisis wasn't to "streamline" continuity - actually, it didn't do anything at all to continuity, which remained much as it had ever been, a jumbled mess of contradictory signs that could make sense or not depending on the readers' own disposition. Everything before Crisis #10 still happened, after all, it just wasn't all remembered, and what was remembered was significantly altered. This process was - and should have been - left largely to the discretion of individual creators and editors. The real point of Crisis wasn't - or shouldn't have been - to lay down ironclad rules for future storytelling. It should have been used - and from what I've read of Wolfman's own words, this was more along the lines of his own intentions - to construct a platform on which new stories could be told without having to be hogtied to continuity. "Streamling" implies a continuing obeisance, whereas Crisis should rightfully have obviated the compulsion altogether. Of course, such a statement is incredibly naive, both on my part and on the part of those at DC who dedicated many years of their lives to making the post-Crisis status quo work as well as it did. You can't build an expectation of strict consistency over many years of publishing and then suddenly expect readers to abandon the practice when it becomes no longer feasible to do so. The fact that many creators were likewise invested in this kind of minutiae became increasingly problematic.****
It might seem like a fine point of distinction, but just cast your mind back on all those endless, pointless stories told in the decade after Crisis which were specifically dedicated to untangling some mess or another of garbled continuity. Wolfman & Perez themselves specifically stated how the post-Crisis discrepancies should be resolved by providing a simple mechanism by which New Earth could right itself. In Crisis #11, right after New Earth is created, a number of heroes still have memories of the multiverse - including, obviously, the Earth-2 Superman, Robin and Huntress, who are still alive and awake in the present to find their entire histories completely erased. By the end of the next issue, all the Earth-2 characters whose existence was specifically obviated by the end of the multiverse have faded from existence and are entirely forgotten by the surviving heroes. Soon enough, the Superman revamp that followed meant that there had been no Superboy or Supergirl, either, even if these characters were explicitly not erased by the Crisis - everything that happened prior to Crisis #11 which didn't jibe with the new, still-developing status quo dissipated from the living memory of the characters involved. At first I thought the fact that characters in the last two issues of Crisis still retained their previous Earth 1 status quo - Lex Luthor a convict in jail, everyone still remembering Kara - was a mistake. In reality, it was simply a result of the fact that Wolfman had no idea what the post-Crisis was going to look like. But really, it was smarter than that: after Crisis, everything was still changing, memories were still being updated to reflect New Earth's new timeline. Lex Luthor was a mad scientist in Crisis #11 but when the final aftermaths of the Crisis faded, he had never been anything but a crooked businessman who also happened to be a fairly brilliant scientist on the side. Makes perfect sense, just don't get so hung up on the details of who remembered what when.
Robin II & the Huntress' bodies were never found after they died - nobly! - during the Anti-Monitor's last assault on Earth, and that was an example of the universe righting itself to eliminate any reference to a past that no longer existed. Superman mourns Kara in Crisis #12, but soon enough he wouldn't even remember her, because under Byrne's hand he had no cousin and wouldn't again for another twenty years. it might seem like hand-waving, and - yeah, no way around it, it is hand-waving. But if the last twenty-five years have taught superhero readers anything, it's that sometimes hand-waving is the best response to irreducible complexity. The folks who made Crisis gave every creator who succeeded them a potential "out" in terms of complex continuity patches, but unfortunately not everyone had the good sense to take them up on the invitation. All they had to do was blame any problem on the growing pains of New Earth, certainly a more poetic solution than Superboy Prime punching his way through the fabric of time. Even when, fifteen years after the Crisis, Grant Morrison & Co. specifically labeled the hand-wavey phenomenon "Hypertime"- providing an explicit in-story explanation for why things that didn't precisely "fit" didn't have to be rigorously explained - people still didn't "get" it.*****
The new Hawkman doesn't jibe with the Hawkman in that old Superman annual? Well, never reference that annual again, or it was Adam Strange who did it - doesn't matter, don't pick at the scab! Wonder Woman didn't exist in time to found the Justice League? It was Black Canary - doesn't matter, don't pick at the scab!****** Superboy was necessary for the formation of the Legion of Super-Heroes? Well, uh, I dunno - OK, that one is more difficult than Hawkman, but I'm sure a solution more elegant and functional than "Time Trapper's pocket universe" could have been devised.******* The ultimate solution was, in that instance, to throw the baby out with the bathwater, i.e., razing everything and starting from scratch with Zero Hour. That franchise, long one of DC's most popular, never really recovered from Crisis, and although there were certainly other factors involved in the book's steady decline, the loss of momentum from the constant late-80s continuity patches certainly did not help.
* I thought about this while composing this essay, and I don't know any better way to say it than that, before a certain point, there was a feeling at the time that characters and concepts which had outlived their usefulness simply faded away into the ether, barring some extraordinary act of resurrection, a la "The Anatomy Lesson." Now, of course, we live in a world where comic book companies are primarily media companies, and every character - no matter how insignificant or obscure - is a potential blockbuster property. This is a world, after all, where Blade can appear out of nowhere to gross hundreds of millions of dollars - so nothing is really outside the realm of possibility, particularly if you're an ambitious media executive. Nowadays its far more probable that a comic company might oversell the value of its intellectual property (remember when that phrase entered the lexicon? remember how it seemed almost like an oxymoron at first, until it was gradually accepted?), than ever consciously lowball potential lucrative "franchises-in-waiting." In the 80s, however, it definitely seemed as if events like Crisis were specifically designed in part to put certain concepts into the proverbial mothballs - and the fact that, for all the oddball properties that have recurred in one shape or another, there is still a huge percentage of DC characters who haven't been seen since '85 or '86 proves my point.
** I know that in most of these cases the characters remained mired in some red-tape for prolonged periods of time. I know that certain of the Fawcett characters weren't completely cleared for continual use until pretty much right before Crisis was published, for instance, and the Charlton heroes weren't brought into the fold until the early 80s when the company liquidated much of it's IP. Someone in the comments might know more about the particulars than I - it wasn't all as cut-and-dried as a simple explanation might imply, but the long and the short of it is that many of these characters were, by 1985, free and clear for the first time.
*** Of course, the first post-Crisis Shazam revival by Roy Thomas was pretty dreadful, but in fairness he's a hard character to get right. Is he better served by remaining in continuity-free or continuity-lite contexts such as that Jeff Smith series, or the recent all-ages Johnny DC series? Probably.
**** Again, the difference between "continuity" and "consistency" is important. Even if it sometimes appears as if the words can be used interchangeably - hell, I do it all the time - they really should be used to refer to two different things. I would like all my comics to be consistent, and certainly continuity is a tool - the major tool - used to achieve this consistency. But continuity is only a tool, and if strict observance of continuity gets in the way of telling a good story, I'm more than willing to accept some hand-waving and a nod in the general direction of consistency without necessarily inferring anything in the way of nefarious intent on the parts of those creators who feel the need to sidestep continuity. I, of course, reserve the right to still get pissy when someone or other contradicts my favorite old issue of Quasar in order to puff up their Sleepwalker one-shot - but that's a fan's prerogative, and no sane creator should feel compelled to cater to my particular tastes, especially if the results are generally to the good. But it should also be pointed out that the number one responsibility of any creator writing in these shared universes should be to use their characters as respectfully as possible, so that any changes made in the service of the story can ultimately be rationalized as having been for the good. (This makes sense not just from the perspective of a fan or reader, incidentally, but from that of a business as well: a company that makes a habit of treating its characters with disrespect is ultimately eroding the value of their own IP in the name of short-term gains.) Undoing decades of characterization and continuity simply because they seem superfluous or unwieldy, on the other hand, is just petty and lazy - especially when, as is the case with Doctor Strange, to name but one - these kinds of radical "reshuffling" exercises are not particularly respectful or even very effective.
***** For all the crap that Marvel got over the nullification of the Spider-Marriage - and yeah, the solution was monstrously inelegant, thoroughly troublesome, and created far more problems than Marvel wants to acknowledge - it was a necessary evil, a quick plot device necessary to hand-wave away a plot element that was perceived as increasingly restrictive. Their reaction to complaints, especially in the wake of O.M.I.T., has been refreshingly healthy, even if their public tone has been unnecessarily caustic at times: don't sweat it - enjoy your favorite back issues with the status quo you prefer, and hopefully also enjoy the comics being published today. But don't get upset if they don't match-up 100%, because the creators and editors are not going to make absolute consistency their priority.
****** And certainly don't try to send Wonder Woman's mother back in time in order to retroactively insert her into the JSA after she had been explicitly written out of the Golden Age period by many successive creators - unless you just like pissing off people for no reason. I realize that by my own rules I should just be happy to "hand wave" the consequences away - but honestly, I think it was just sort of petulant to undo something that really did upturn far more apple carts than strictly necessary. Just because continuity should be pliable doesn't mean people should go out of their way to complicate attempted consistency.
******* On the top of my head, a better way would have been to incorporate a few elements of the retcons that were utilized in a far more painless and definitive manner than what actually did happen. It is, after all is said and done, pretty essential to the history of the Legion that Superboy be present for their earliest adventures, true. But the way to get around that in the immediate wake of the Crisis and Byrne's new status quo would have been to have some sort of accident at the Time Institute following the event after which the group of core Legionnaires - let's say, the dozen most prominent characters, Cosmic Boy, Lightning Lad, Saturn Girl, Brainiac 5 and the like - clearly remember the pre-Crisis status quo - including Superboy and the multiple earths - but everyone else in the 30th century world from that moment forward can only remember New Earth continuity. All references in the history files to Superboy and Supergirl have been replaced by Mon-el and Lar Gand, and the ancient 20th century Superman is only a historical role model for 30th century heroism. So even though the original Silver Age stories still "count," you would also have the pathos of the core Legionnaires being the only ones who remembered that their friend Superboy ever existed, or that Supergirl was ever Brainiac's lover, etc etc. It would have been slightly messy, admittedly, to have such a large group of characters still remember the pre-Crisis multiverse, but if it was a choice between that and what actually did happen to the Legion, well, I think a little messiness would be a small price to pay.