Would the Star Wars sequels have been better if they were filmed 10 to 15 years earlier

Not necessarily but there maybe should have been a better release order to the movies/TV shows. There probably should have been a live-action "Empire Era" TV series released a few years after Revenge of the Sith. Then Rogue One should have been released as a sort of "big finale" for the prequel era of Star Wars with Carrie Fisher's appearance at the very end as hint that the sequel trilogy is on the horizon. Then do Episode VII and have Solo be the spin-off film that immediately follows since audiences would still be riding off the high of Force Awakens and the return of Harrison Ford as Han Solo and then do Episode VIII and IX but not the same two films we ultimately got.

I think so. The 3 actors you mentioned above would still be old, but at least the story-telling would have been better.

Yes...more like 25-30 years earlier.

George should have done the sequels in 1999, 2002 and 2005, Ford, Hamill and Fisher all looked good back then, and it would have had the Star Wars creator at the helm with an original story and not be fucked up by Disney.