I find Ep 7 to be mostly unwatchable because it’s almost all fan service without a real story to be found. There was no plot for Ep 8 to hang itself on, just a few coathooks widely spread.

Ep 8 had some really interesting character arcs, but also made some basic errors. As a movie, I think that it’s the strongest of the three sequels. Given a lack of plot points to really hang off, Johnson seems to have done something interesting, but left even fewer plot points to hang off than Abrams left him. Let’s be clear: if Lucasfilm had disagreed with his direction, they would have taken him off the project.

Ep 9 was more fan service (who can we throw into this scene?) with an even more inexplicable plot hook (if the Emperor was coming back in any way, there should have been hints of that in Ep 7).

I do not understand the fascination with J J Abrams. He claims to be a fan of various media, but IMO he is the shallowest type of fan out there, appreciating only certain aesthetics without looking any deeper. His Star Trek films are the absolute worst of all the Star Trek films, even worse than Star Trek V: The Final Frontier. Why are they the worst? Because they have become Generic Action Films with a Star Trek veneer. (This is more or less my complaint with Picard.) I dread the idea of seeing J J Abrams touch any more science fiction properties because he just doesn’t get them and turns them into Michael Bay films (but with lens flares instead of explosions).

I do agree with you that Disney mismanaged the whole trilogy, and the fault lies with them. They very clearly went into it without any sort of plan or even a particular vision, deferring completely to whatever each director wanted to do. With minimal imposition of a plot outline, the whole thing could have gone much better, even while still leaving the individual directors to mostly decide how they got there.

To my mind, letting Abrams double-down on swerving back to his plot in episode 9 was their biggest management sin when it comes to creating a coherent plot arc. If they'd carried on with what 8 was setting up we'd have had ["nostalgia" => "twist" => "resolution"], and instead we were left with ["nostalgia" => "twist" => "ignore that! more nostalgia"]. The former could have worked out and won over those who disliked the Last Jedi twists, the latter just flopped unsatisfyingly. (A second-movie twist was always in the cards, given general fan sentiment about Empire.)

Disclaimer: I personally liked episode 8 the most of that trilogy, and it's the only one I'd bother to go rewatch. It has the best direction by far, along with the most striking visuals of the lot and most of the quotable lines. That said, I think my take on this holds up regardless of which side of the Last Jedi divide you fall on. :D

And Disney could have said "no" to any of his ideas at any point. He's become a scapegoat for bitter fans who can't see that Disney didn't know what to do after the first movie.