I equate it to the infinite realities theory.
Like, yes, there's a reality where Peggy Carter becomes Captain and does everything Steve did and the universes are essentially the same. AND there's a reality where Peggy becomes Cap and dies in her first mission. AND a reality where Peggy becomes Cap and becomes the leader of Hydra. The possible realities are endless and they're choosing to focus on the first one because that's the story they want to tell.

I think Rick and Morty handles this extremely well.