Yeah, I think the two biggest weaknesses in the MCU are the weakness of most of the "super" villains, and the introduction of some many heroes without being willing to kill one off.
I'm personally hoping for a Captain death. I know it's happened a ton in the comics, though I'm not a comic reader, and I think it makes sense in the MCU both story wise and real world. Evans has talked for a while about wanted to move away from the character, I don't think he can "retire" in the MCU as that's just not how Cap is built, that is easily the impactful moment that can bring the others back together, and if done right would really hit the audience. So that's my vote, though as NR says, may never be allowed.
I also think Start starts to step back at some point as they move to new characters, but he can be kept in the MCU and retire or move to an advisory role that just has some cameos. I think that can be explained in the story pretty easily.