think the single hero movies are necessary though. Fact of the matter is that the 2nd and 3rd Iron Man movies and Thor and Captain America were not that great. I think they retroactively got better when the Avengers movies brought everything together as if it was one big storyline. The movies got better because they didn't have to be the greatest but were part of something that really hit the right notes in the team up movies.
I'm hoping the same thing happens with these movies and I suspect they will.
The other problem is Avengers 3 and 4 were just really good movies for this genre. There was really no way to stay that high (although No Way Home was really good as well. Just my opinion.