Because YOU demanded it: Extended dourness and turgidity.
I mulled over my thoughts on the Snyder cut of JUSTICE LEAGUE for the past two days, and after sitting through its four-hour run time, I honestly have to ask myself why I even bothered. The immediate answers to that would be 1. So I could speak on it from a fully-informed POV, and 2. To see any new or extended footage involving Diana — yeah, I'm a total Wonder Woman mark — but it really was not worth the time expended. Yes, it's a more coherent piece than the theatrical version and it is very much the work of one director's vision, but an extended mess is still a mess, no matter how much you tart it up. Also, there was no way in hell that any American studio would release four hours of this to theaters and expect to turn a profit. Hell, they even balk at a feature that's just a bit longer than two hours, so four hours? Forget about it.
Yeah, it does flesh out the characters to a much greater degree, but when you have what's basically a pack of either boring non-entities or characters that the director fundamentally does not understand at all, such fleshing-out is about as effective as pissing into a hurricane. And though this version excises the jokey material that was clearly the work of Joss Whedon, what results is a dour, dark, and depressing effort that feel like a four-hour iteration of the Bataan Death March. DC and its stable of superhero characters have always been light fare, some would not unfairly describe them as "whitebread," and what Snyder gives us is an angsty emo kid's take on them. There is neither fun nor joy to be had here, and even the resurrection of Superman is accompanied by the black version of his uniform. As if the film's overall color palette were not already drab enough, we get comics culture's most iconic exemplar of raw power wielded with hope and kindness showing up like he's ready front for My Chemical Romance. At least Darkseid is actually in it (not that he does anything) and the visuals on Steppenwolf are considerably improved.
And speaking of Superman, following the events of BATMAN V SUPERMAN, the entire world knows that Superman was dead and, to a lesser/more localized degree, the same goes for noted Daily Planet reporter Clark Kent. In JUSTICE LEAGUE, when the heroes use a Mother Box to revive Supes, he returns in a confused and aggressive state — as seen in the theatrical version — and both Batman and Lois Lane call out to him as "Clark," and they do so in front of an assortment of police officers and military personnel, thus outing Clark to numerous witnesses. And once the story wraps up, Clark Kent is suddenly back from the dead at the same time as Superman and no one finds that odd?
There really are no spoilers for this version, as it's merely the theatrical excised of the Whedon material and taffy-pulled to a nigh-interminable duration. The post-apocalyptic vision of a world in which Superman has gone bad is also lengthened and it serves zero narrative purpose since a sequel to this will hopefully never happen. In that sequence Batman leads a team of Deathstroke, Mera — who's toting around a couple opf gallons of water in an otherwise arid landscape — and Jared Leto's horrendous take on the Joker, now seen with long hair, smudged lipstick, and spouting a whole lot of nonsense that will never be paid off. Oh, and we also get two brief scenes where the Martian Manhunter shows up, but he serves little or no purpose in the story other than to announce his presence and, while in the form of Martha Kent, get Lois off of her grieving ass and motivate her to return to work.
If none of this sounds compelling, it's because it isn't, and you are advised to spend four precious hours doing something, damned near anything else, other than sitting through this glacially-paced monument to the power of fandom and its ability to bully a studio into making you see the same garbage twice, only now with more garbage to pad it out. For completists only, and maybe not even then.