I don't know why you are comparing Star Wars to Marvel or superheroes? Star Wars isn't even based on comics.
How many times have Spider-Man, Fantastic Four, Batman, and the Hulk have been rebooted in the last 20 years?
Because what they are based on is irrelevant to me. What does that have to do with rebooting? Why would being based on comics warrant more reboots?
And yes, those characters have been rebooted a lot. But
should they be? Was it a good thing that Maguire's Spider-Man got rebooted into Amazing Spider-Man?
I think that an important distinction here is also that all the franchises you mention are about specific characters, while both the MCU and Star Wars are about a universe that happens to have some important characters in it. You can't keep a Batman franchise going indefinitely without Batman. But you
can kill off Luke, Leia, Han, Obi-Wan, Anakin, Yoda, etc. forever and then just make up some bounty hunter named Din Djarin and make him a new protagonist in the franchise because the franchise is not called "Luke Skywalker", it's called "Star Wars". Same for the MCU. It doesn't have static main characters that the franchise has to rely on. It can pivot to other characters.
And if you really wanted to do something with Iron Man or Captain America you wouldn't
have to do it as part of a Cinematic Universe and take the entire established universe down with it. DC has their own cinematic universe and yet they made Joker and now a standalone Batman movie is coming out in a few months. If you're really worried about the next generation of children not growing up with a Tony Stark or Steve Rogers and they're no longer in your cinematic universe, give some director who has a cool idea or vision for one of these characters the opportunity to make a standalone movie about them that doesn't require any other viewing. Make it as stylistic as you want without worrying about it fitting in the established style of the rest of the universe. Take more risks and write more radical stories because you don't have to worry about ripple effects. We've had Spider-Man, Ghost Rider and Fantastic Four standalone movies while the MCU was already ongoing, we can have that again. Or make an awesome animated movie for them like they did with Spiderverse. Be creative, the sky's the limit. No need to take down the entire MCU just to put one or two characters in a movie.