I believe the fault lies with Disney and the make-believe “Lucasfilm Story Group” that they created
I just want to say I really appreciate you giving such a measured take on the situation.
It’s Abrams’ fault. It’s his name on the movie, his name as producer, his name as writer. He made the movie. Acting like a larger plan would have stopped him from making a bad trilogy-ender doesn’t make any sort of logical sense (almost as little logical sense as saying the story group was “make believe,” or further, thinking the story group was anything but canon checkers for the creatives). He abandoned “the plan” TWICE when making TFA (both Lucas’ notes and then Arndt’s treatments) and it became a much-loved, well-reviewed success - the highest grossing (domestic) film in history (and likely will be for the foreseeable future). There being “a plan” for The Rise of Skywalker wouldn’t have mattered one whit, because when he did get the chance to come back, he ignored HIS OWN PLANS (Rey Kenobi, Finn the Jedi, Stormtrooper rebellion) to pursue something completely different. And it didn’t work.
Had Abrams made a good movie out of his new on the fly plans (like he did with TFA), none of us would be talking about plans, or “executive meddling” (he’s the executive doing the meddling at the behest of other executives, btw). But he made a bad movie, and now we’re all trying to figure out how it could have happened. But the truth is it happened because nobody bats a thousand. He’s made bad movies before, and he made a bad movie again, this time to end the sequel trilogy. The idea that Disney could have stopped that with a “well conceived plan” doesn’t make any sense. It’s wishful thinking. The dude doesn’t follow plans no matter where they come from, even if “Following the plan” were some surefire key to success, and it isn’t.
Every movie is a risk, and there isn’t some cheat code or safety net to prevent bad movies from coming out of the creative process. It takes work, talent, collaboration, skill, and luck. Every time. No matter what the plan is.