I absolutely think the art direction in Injustice 2 is stellar. My most immediate gripe with NRS games since MK9 gave them a big, big comeback has been that the art has tended to look janky. If there's anything that continues to bother me about the art in Injustice 2 in particular, it's that the vast majority of costumes look kinda corny -- aside from some of the characters that dress closer to a plainclothes look, it feels like the costume direction leans a bit too heavy on being "cinematic universe" inspired in design, and there feels to be something of a lack of "comic book inspired," in the strictly "leotard/tights" sense, anyway. Even if it did look a little off being matched with the more photorealistic facial designs, I'd still appreciate if those types of costumes were shown off more frequently (and perhaps they are in fact in the game, they just haven't been marketed often).
The now-famous YouTube video that breaks down the animations really did hit home for me, and funny enough, I had actually never really given the animation a ton of thought, as I kind of expect Mortal Kombat in particular to sort of move in a hammy way. However, sort of seeing the logic behind why it bothers people made it a lot more apparent to me than it was before. It's not wholesale dismissal of NRS' animation systems, though, as some particular animations and sometimes even whole characters seem handled well, but it's certainly uneven IMO.
That said, I'm still grabbing the game on Tuesday, I've been excited for a while now and I've been glad to see the art direction and character modeling improve over time of this game's development.