Yeah you’re right, they were so afraid of that happening, but instead of accepting it and leaning into it they went in the opposite direction. That’s the problem. If you create Star Wars movies with the original cast returning, everyone is going to be there to see the original cast. If you do include them, it’s impossible for it to be any other way. The way you legitimize the new characters is to graft them on to what is already there, not try to have them compete in a zero sum game they’re always going to lose.
2015 was such a different time. People really were open to, at the very least, Finn being the main character and becoming a Jedi. TFA was a “good enough” movie on its own because it felt like it was really going somewhere. I think part of that was seeing the interactions with Han and anticipating the interactions with Luke.
With Indiana Jones I think it’s a special case where you simply can’t have anyone other than Harrison Ford in the role, and that goes for new characters too. As weird as it sounds I think their best chance at actually making a good movie would be to make a spinoff about adult Short Round, instead of trying to make someone who is sort of a new Indiana Jones but not really. If Shia Labeouf were way more charismatic I think it would be better, but that’s really not fair to him because it’s probably impossible to become just as iconic a character as Indy himself.
I think it is fair to say that the prequel characters were inheriting the OT, given that most of them were the same people, just earlier. You’re watching the whole thing to find out how Anakin becomes Vader, who you’re already very familiar with. Obi Wan is there, Yoda is there, the Emperor is there. The primary additions are Qui Gon and Padme. As many have said, this nostalgia bait is actually done way too much, to the point of also shoehorning in Boba/Jango Fett, Jabba, C3PO and R2D2, and Chewbacca where they don’t belong.