The “girl power”
The amount of “girl power” moments ... like Pepper Potts in an Iron Man suit, the female characters teaming up for a moment in the final battle, Scarlet Witch single-handedly overpowering Thanos (who only survived by calling a missile strike), Captain Marvel (once again, dominating Thanos until he used an Infinity Stone), Valkyrie becoming king of Asgard... were eye-rollingly forced and unsubtle.
I would have traded all of them for some actual character development and action scenes for Black Widow, who basically committed suicide because Hawkeye had a family and she didn’t/couldn’t.