Without wishing to trigger a raft of "faaaaaanbooooooy" chants, there isn't much that Marvel has got wrong over the last few years. Yes, we've personally pulled up some plot holes and logical gaps in the narrative, but in broad strokes, everything usually averages out a success. But given the number of films and the sheer amount of time that has passed, a lot of these decisions tend to get made on the fly.
Whether it's production issues, casting problems, or just flat out changing their minds, the MCU has needed more than a few course corrects over the last decade. By and large, they've gotten away with them, but a few just haven't quite sat right when watching in hindsight. Unlike the Avengers themselves though, Marvel Studios are not blessed with a time machine and just have to live with these decisions.
But what if? What if they could have their time back and rewrite, reimagine and even recast some of their iconic heroes and villains? Who would be top of that particular list, and how exactly would they want to change them? Well, based on... uh... everything since, those answers are glaringly obvious.