I get that there are contracts involved and actors just wanting to do other things, but in retrospect taking Cap, Iron Man, AND Black Widow off the table in Endgame was a mistake. It maybe wouldn't have been so bad if they hadn't reduced Thor and Hulk to pure comedy characters, but they did. The end result is you basically had no OG Avengers to build around.
I've been doing an MCU rewatch and what strikes me about the early stuff compared to a lot of the later stuff is how much less GOOFY it is. It's quippy. There are jokes and repartee and the like, but it'd not just aggressively silly like so much of the later stuff has been.