First, awesome riff on the Kenobi quote.
Second, is Lucas really that interesting? Outside of the pathological fear of women that crops up in the imagery and storyline of every film in the franchise--which seems to be transparently rooted to the failing marriage he was in at the time of the original films and subsequent divorce--the story of Lucas seems to be really, really simple: film is a collaborative process and when you tune out all your collaborators you are going to turn out shit films.
As you point out, that also seems to be where Jackson and Shyamalan started to go bad, when they achieved a level of success at which they no longer had to listen to anyone. These all seem to be pretty straightforward stories of hubris.
By the time of the prequels he's reached the point every director or creative artist probably dreams of, pretty much total autonomy, but conversely without challengers the final product is all the weaker for it. If he'd gone with the prequel scripts before the OT looking for investment he'd have had to get the scripts polished up a lot more than he did. He was bankrolling himself so he stopped a good couple (at least drafts) before he probably should have.
But then again, as some point out fair fucking play for getting into that position in the first place and why the Hell shouldn't he do what he likes? I think there are lessons there though (from all three directors) that are worth talking about.