I know the studio is technically calling this "Zack Snyder's Justice League," but let's not delude ourselves into pretending this will be remembered as anything other than The Snyder Cut. Besides, the prefix "Zack Snyder's" implies the theatrical cut belonged to someone else, and perhaps the largest reveal of this incarnation is that's not really true. Obviously Snyder (no relation) wasn't happy with the original (who was?), but most of the scenes I assumed had been written and shot by Whedon apparently weren't. Likewise, the paper-thin mulligan hunt forming the narrative backbone remained unchanged. In short, this is less a complete reconstruction of the 2017 flop than a conventional extended edition. It's just... really, really, really extended.
I'm something of an anomaly among film fans and critics, in that I have no issue with movies being long, provided that time is well used. If you're telling a complex story, developing a detailed world, building out interesting themes, or even constructing an elaborate tone, I'm happy to invest almost any amount of time in a project.
Here's the thing, though: The Snyder Cut accomplishes none of these things. Other than a couple expanded arcs, the story is the same as it was in the theatrical. The world, while definitely improved, was still underdeveloped. The themes... don't make me laugh: this is still "Justice League: Friendship is Magic," but now it's Friendship is Magic with the occasional decapitation. Theme is not Zack Snyder's forte.
That brings us to tone, which I suspect is the aspect most of this movie's fans will point to in order to justify its length. Because it's true the movie does, in fact, have a tone. It does not, however, build that tone, subvert it, or use it to meaningfully enhance its story (again, there's barely a story at all). The tone is present at the start, it doesn't evolve or change much, and it sticks around through the unnecessary epilogue. That same tone could have been easily injected into a two-hour movie, a 60-minute TV show, or a music video (and if you've ever seen a Zack Snyder movie before, you won't be surprised to hear most of this feels like a series of music videos, anyway).
In short, this didn't need to be this long, and it doesn't really gain anything from that length. There is, however, some good news. Taken on its own merits (which, again, is tough to do since it's mostly the same as the theatrical cut), this is largely an improvement. More importantly, it's far, far, far better than Batman v Superman. Infinitely better. That movie was trash.
I glossed over the characters above, but this does a better job with most of its leads. Flash, in particular, is delightful - he was a standout in the theatrical, as well, and most of those scenes made it into this installment, as did some fantastic new ones. Flash's powers work perfectly with Zack Snyder's visual style - if there's a reason to sit through this, it's for the Flash scenes.
I wasn't as head-over-heels in love with the new Cyborg material as some reviewers, but the character is definitely better treated here than in the last version. I do like the sequence where he uses his powers in a Robin Hood capacity. The rest of his arc is fine, but mostly I found it boring. Your millage may vary - like I said, this interpretation of the character is definitely picking up some fans.
After Flash, I actually think Batman benefits the most from this cut. It wasn't so much more material than the fact the darker tone means his optimism shines through a little brighter. A smirk here and there means more in contrast.
Wonder Woman and Aquaman didn't get much out of this - there's some new footage, but I don't feel like it adds up to anything more substantial than we got from the previous installment (besides, they both have solo movies that are far better than either version of Justice League).
Superman is notable in that he gets significantly less screen time here than in the theatrical, which was surprising. For what it's worth, we still get a happier, more hopeful Superman than we saw in Man of Steel or BvS, if only briefly. In other words, this is a truncated version of Superman from the theatrical Justice League.
Steppenwolf is more interesting here, though still underwhelming. He's less a generic villain and more a pitiful, desperate monster trying to get home. This doesn't really go anywhere or pay off, but I guess it counts as an improvement.
The action scenes are generally improved, but get ready for some caveats. The movie has some great moments where the concepts and effects come together and deliver some truly awesome visuals. But it also has a bunch of sequences where actors in bulky costumes cut to obvious CG cartoons, breaking the flow. In addition, the movie continues to mistake brutal for cool, which undersells the value of the characters being adapted. It also drives home the fact that this is not, in fact, a movie for grown-ups.
I could go on, both nitpicking and complimenting various sequences or elements, but I don't feel the need to indulge in a Snyder-cut of my own. Ultimately, the nicest thing I can say is if I were advising someone who'd never seen either version of Justice League which to watch, I'd point them towards this one. The meanest thing I can say is if I were talking to someone who'd already seen the theatrical, I'd tell them they could skip this. It's not awful, but it really just doesn't add that much of value, especially weighed against its runtime.