One surprisingly candid bit in The Skywalker Legacy doc was that they seemed to land on the idea of the dagger map pretty late in the game, and couldn't decide what the macguffin to point Rey to the Death Star ruins should be. You see JJ go through other props, like a scroll and a few other things, and just can't figure out how to crack it. Also interesting that the VFX artists who created the Death Star ruins originally had the whole dish sitting in the water intact, and JJ thought that was too on the nose, haha
Hearing him talk, he really does sound thoughtful. I honestly think both movies have a few good ideas that sound great when he describes them. But he isn't the director, a producer, or the money man. He brings the ideas, but he doesn't have final say. He understands the themes and the power of the ideas, but if JJ or KK or anyone above him says "but nah we can't kill Chewie" then that's that. I find it hard to blame him for anything when the faults of BvS and TRoS really are very distinctly borne from the "vision" or storytelling tendencies of Zack Snyder and JJ Abrams.
I don't mean in terms of story ideas or plot points; almost everything he talks about in a plot sense in the doc is in the movie anyway, with the notable exception of "when the Dyad comes together for the light it's more powerful than we imagined." I meant more in terms of how he frames certain story decisions, referencing Arthur Miller, referencing Campbell, etc. It's this erudite projection onto the work that isn't actually reflected in the work. Going back to my 3PO example, he frames the sacrifice of 3PO's memory as this big blow to the story, that 3PO was the keeper of the tale, that him losing his memory is like the opening crawl dissolving. And he frames it in this really weighty manner and it never comes off like that in the actual movie.
On BvS I think Terrio just wrote the script and was hands off after that. But on TROS he seems like a pretty close partner of JJ's, he's seen on set all the time, etc. And he even talked about this in an interview iirc, where he had far more creative involvement and partnership with JJ on TROS compared to his work on BvS. In any event, when you have these two maligned big franchise movies where the common thread they share is the same screenwriter, I'm inclined to think that writer is at least somewhat culpable lol.
They brought him back because somewhere along the line JJ got it in his head that they had to tie all 9 films together and he was the link. If he was going to come back I would have preferred it that he was some sort of spirit. Like the dark side attempt at force ghosts.
This was also touched on in the doc, I can't remember if it was JJ or Terrio (I want to say Terrio though), but one of them said something like bringing back Palpatine seemed like the logical conclusion because Star Wars is a multi-generational story about Skywalkers and Palpatines. And I was like...
no it isn't. It only became a story of Skywalkers and Palpatines because TROS made it that way!