The movie fell flat on several levels for me:
1) The climax was LITERALLY the same as the prior film, only with a reversed outcome that was completely anticlimactic and unsurprising as it was narratively necessary to give the story ANY possible modicum of justified production.
2) Stark has ABSOLUTELY zero reason to sacrifice himself, given the presence of several other more powerful heroes, such as Thor, Captain Marvel, and Scarlet Witch, who could have wielded the Gauntlet without overloading
3) Thanos was reduced to a completely generic villain (although his initial Malthusian motivation was nonsensical to begin with) who wanted the omnipotent MacGuffin to destroy the universe, no different than Ego, Hela, Dormammu, and numerous other prior MCU villains. He could have been given a redemption arc, seeing the negative consequences of the snap and helping the heroes defeat an alternate version of himself to reconstruct the Gauntlet and protect the world from his alternate's new invasion plan. Instead he was more generic than Whedon Steppenwolf
4) The film lazily uses time travel to resolve all of it's problems even though Thanos, the Time Variance Authority, and/or the Illuminati should have complete control over time
5) The film ignores Agents of Shield although it's heroes are more than ready and qualified to deal with this situation (arguably BY THEMSELVES), and that's NOT INCLUDING the Defenders, Eternals, Egyptian/Omnipotence City Gods, or Runaways
6) The film only barely deals with the consequences of the Snap, whose effects are never made clear, as "50% of all life" could mean "50% of the dominant species", "50% of the biosphere", "50% of both genders/100% of one gender", "50% of the universe's habitable planets", etc....
7) The "female teamup" scene (and Shuri insulting Banner) was unbearably obnoxious feminist bait. Whereas in Infinity War, the Proxima Midnight fight was both empowering yet narratively organic, the scene in this felt more like demographic pandering than that bad Kardashian Pepsi commercial imo.