Endgame was a nice reflection on the MCU to that point, but it felt a bit like a letdown. The plot felt safe and predictable for the most part. The 'heist' was more of a wink and nod then really interesting of itself.
Infinity War though is the masterpiece. Really no weaknesses in that movie. Able to move a lot of pieces, deliver some great action, but also move a giant plot forward.
**What I would have done is a heist/chase movie. Each time the avengers go back in time to find a stone, Thanos shows up and beats them up. The avengers escape to another time period, losing members, and Thanos on the pursuit. You could have fun scenes of the future Avengers trying to convince the past Avengers they are really are on the up and up. Eventually in the battle of NY, Thanos takes command of the Chitari, but Iron Man forms the gauntlet....hesitates snapping his fingers, but then sees his past self flying the nuke into the wormhole...and realizes giving his life to save the world is his destiny.