But the process is the same whether you take years or months.
This isn’t true at all. The process isn’t the same from movie to movie often, much less across multiple decades in an industry that has changed a lot.
The process now is not the same as it was in the '70s. If Star Wars was made then the way ALL blockbusters are made now, we wouldn’t have gotten to draft 4, because when Ladd greenlit it, he’d have greenlit it with a release date locked and everything would have been set to that clock. Star Wars didn’t have a clock put on it until much, much later in the development process. The clock still almost drove Lucas insane, but he got a lot of time to develop that script that is damn near impossible to get now.
It’s a different machine creators are working in. Or rather, the engine and the gears move differently than they did when Lucas was around. Lucas is partially the reason that machine now operates the way it does, thanks to his efforts in the early 00s. Comparing the script development of Star Wars in 74 to Trevorrow’s efforts in 2017 is a comparison that isn’t worth much because not only are the creatives in question pretty wildly different, but the process is also pretty wildly different now, too.
I hate to keep harping on this point, but I have studied a bit of Hollywood history and nearly every movie goes through rewrites. The bigger they are the more often it happens. Gone With the Wind had many rewrites. The Lord of the Rings trilogy had many rewrites. 80 years pass and not much has changed. About the only thing that has is there are more edits during production now with reshoots going from a rare thing to commonplace, even normal. So that is just one more time that a movie can get edits. And I’m sure they edit the script to plan out their changes. It is the guide for how the movie is filmed and put together in the edit. So whether Lucas had 3 years from first draft to final edit and on TFA Abrams had 2 years and started with Lucas’s, the end result is the same. That applies to IX as well. It is clear from this early draft that Abrams did not just throw it out, but edited it to get to the story we have. The story beats are all pretty much the same, like Lucas’s early drafts and the final movie. Some things changed a lot and some carried through. If you study enough script development you’d know this is absolutely normal when creating a script. And even adaptions go through this to find the right way to turn novel to screen. LOTR went through a few shorter drafts before being expanded back out. If you think anything any Star Wars movie has done script wise is unusual, you haven’t studied enough of the process. Each one is absolutely normal, whether you look at the 1930’s, 1970’s, or today. It is just part of the creative process of writing and making a movie.