I think also what Marvel has done is they obviously have one huge franchise but they also have several sub franchises. Each hero is his own franchise. That helps prevent it feeling like they are seeing the same thing. I mean they started with Iron Man, if they were on Iron Man 18 now I don't think theyd be doing as well.
I was actually going to post something related to that about Star Wars. Basically thus far there has been "Star Wars", I think what they are doing is trying to create different franchises inside Star Wars. I mean even this Solo movie could spawn a franchise. If Solo is well received then why not release "Lando" in a couple years, then "Solo 2" after that and eventually bring the 2 back together.
I think Disney realizes that if they keep making Star Wars movies that eventually they will start making less money. Eventually they will have a movie that makes 180 mil domestic like Ant Man or 230 like Dr Strange. But they also know that once in whlle one will hit right like Black Pather has and it will go crazy.