Spoilers
I finally gave this a spin, having read and watched nearly all the spoilers, and expecting watchable mediocrity. Instead... woof. It's terrible. Watchable, but only barely, thanks largely to Gadot and the sheer car-wreck fascination factor.
The story is a shambolic, half-assed rip-off of The Avengers. (To quote Cap: if any comics experts want to point out that actually, this or that DC thing came before this or that Marvel thing in print: "Son... just don't.") The dialogue is honkingly bad, with the exception of a few decent Whedon cracks here and there. I was genuinely embarrassed by the camera's fixation on Gadot's ass. (Don't get me wrong, I'm all for gratuitous fanservice, but not so much in an ostensibly all-ages entertainment such as this.) Sorry, Bob, the villain is far worse than Hela or Ultron. I have nothing against CG characters - I think Apocalypse should have been one - but Ciarán Hinds has one of the most badass faces around, so WTF is the point of casting him and not at least using his features as the basis for a CG model? CG characters should have exaggerated features, like Gollum or Hulk, to make up for the detail lost without human actors, but Steppenwolf's face looked easily achievable with makeup/prosthetics.
That whole Russian family... huh?
Bruce (who, without his irrational but compelling BvS murderousness, is boring as hell here) only summoning Lois as a "contingency" if the revived Clark freaks out, instead of the default plan... why? And why is her appearance treated like a reveal, when we have that useless scene of Martha and Lois earlier?! ("Surprise! The character you already saw in this movie is in this movie! Bet you didn't see that coming!") Also, Cavill/Supes looked weird, and I don't think it was just the Uncanny Lip. The Lisa Frank Purple-looking suit didn't help, of course, and maybe it was the way its texture made the whole of him look ridiculous at all times, but, I dunno, he looked bad.
And, "Mother Boxes"? Really? Um... No? (And what was with all those gratuitous swears?) Also: I thought we'd left grunge/nu-metal music cues back in the W. Bush years?
Ezra Milller's Barry/Flash was... fine? He was fine. I almost forgot about Cyborg - a nothing character whose design looks terrible, and whose entire role is a poor retread of Vision. As for Aquaman... bleeeaaaarrrrgggghhh. And if Diana can outrun bullets all of a sudden, why does she keep letting the villain smack her?
This wasn't quite a Terminator Genisys or Star Trek Beyond-level fiasco, but it wasn't far off. I've always said that, permissive IP rights notwithstanding, Batman and Superman don't belong in the same live-action universe, nor does Supes belong in a universe with other superheroes, and I feel entirely vindicated on both counts here. I give Justice League, absolutely pathetic end-credits scene and all, what the AV Club commentariat has so sagely termed the "Gentleman's F": a
D+