When the third act truly kicks off and everybody shows up, my jaw was agape. Forget what you know about large-scale war shots in films: this makes LOTR ROTK look like a playset. Because we know so many of these characters, it's almost sensory overload, having your eyes dart from corner to corner on the screen trying to pick out each character. There are little micro-meets here that just kept earning cheers from the crowd. I can't believe how much was packed into that whole scene: Cap being worthy, "on your left", Instant Kill Mode, truly Giant Man hooking one of those space snake/turtle/ship things, "assemble"... just, damn.
The time travel mechanics almost felt like the writers admitting defeat in the face of complications. Specifically the audible dismissal of all previous time travel movies. I'm willing to accept that if all the stones are returned, the diverging timelines no longer exist, and I'm even willing to believe Cap used one last jump back at the end instead of the (sort of implied) idea that he just lived a life within the existing timeline.
The main issue, as you'd expect, is that the movie goes out of its way to enforce hard consequences. We're told Natasha can't come back even with using the Stones, and that makes sense... but we have a time-displaced Gamora running around now. Travel back in time, pick up any version of Nat from within the last five years (the closer to the Vormir trip the better), and boom, solved. Unless, I suppose, that would muck up Strange's only-one timeline...
It didn't really clarify how Thanos managed to both figure out the time travel mechanics for his own purposes, as well as be able to transport so much of his army at once. Oh, and there's the constantly varying power levels all over again: Stormbreaker could kill a fully-powered Thanos last movie, but everybody needed to be involved to even wear him down here.
Chubby Thor was hilarious, and I'm glad they kept him that way throughout. I've read some complaints about it, about how it undoes his character progression from his last two appearances, but it makes sense: he blames himself for not just failing his people, but literally half the universe. I imagine that'd weigh pretty heavily on anybody.
Plus, Korg's back. That's very important.
What I semi-expected before going in was that this would mark the end for me too. It hasn't been a whole day yet, but so far I still feel that way. This put a bow on so many aspects of this series that I don't think I want to go watch any more of them, at least not with the same level of attachment. Spider-Man FFH is doing zilch for me. Maybe BP2 or Strange 2 will draw me back.