I think that talking about the current film model as “sequels” is getting it wrong.
Franchises. The word is franchises. You get franchised characters, remakes, spin-offs, sequels, prequels, movie adaptation from TV shows, sidequels, reimaginings, live-action adaptations of cartoons- you name it.
And Frodo Baggins is to blame. Yes, really.
Because Hollywood has always known that familiar characters and stories are money in the bank- or at least more money than original characters in a film of similar quality would be. The problem was that up until this century, new parts of a franchise had to be started from scratch. Terminator is a big hit? You are bound to want a sequel- but of course now you have to wait until Arnold has a free couple of months in the middle of his busy schedule, Cameron first needs to get off his system a movie about water aliens- and before you know it seven years have passed.
Oh, there were exceptions, your Bond films and so on, but those were outliers- nobody thought the same model could be applied to other movies.
And then you have Lord of the Rings. This was three films with a giant budget that were shot back to back, without waiting to even find out if the first one would bring any money. And it succeeded. The risk paid off and the budget was drastically reduced, since you didn’t need to get new contracts for a new team.
Marvel applied this system to their franchise- got up- and- coming- but- not- there- yet actors like Chris Evans with iron clad contracts not just for the sequels, but related movies, and made films with a long term plan.
This was helped by the fact that the movie star as we know it had pretty much disappeared. Before having access to reviews at the flick of a phone, mostly audiences went to see movies starring some actor they had liked in some other film. This became less prominent and unknowns desperate enough to sign fifteen movie deals, like Chris Pratt, became the new superstars.
Now, personally, if a movie is good, I don’t care if it’s part of a franchise or not. It’s not the end of the world. But if you wanna blame somebody, blame Frodo. And maybe Lucas.