Edit: Overall this movie was good and it's not a flop, it's the second highest grossing movie of the year so far. It's getting a lot of unfair criticizim because of

IMO.
If I have to nit pic, This movie played it safe in every way. Sam was watered down as a hero to make white people feel safe; [no edge no love interest.] End result is a hero that No one finds compelling.
All the anti fascism themes from the first Captain America movies are gone. [Hydra hero registration act]
They don't tell Isaiah Bradley's backstory so You don't get a sense of why it's important for Sam to get him out of prison; the movie lacks stakes.
Japan as the political adversary? Lol.