I don’t believe Lucas ever really had a story for Luke that was interesting in sequels. He had some vague throw away single idea of Luke handing down excalibur to the next generation. But that isn’t a sequel, not really in my opinion if the story isn’t about Luke.

Lucas had used up his original sequel ideas in Return of the Jedi of Luke confronting the Emperor and finding his sister.

There really isn’t anything interesting in terms of conflict and the best Star Wars story was already used in episodes IV, V and VI. The prequels ended up being boring and a backstory that really did not need to be told, and it seems like the sequels never really were even a thing. The story ends on Endor with a happy fairy tale ending.

Lucas could have done something interesting about fathers and sons and generations and had Luke being a teacher and a father, but we all know that wasn’t what he intended. He wanted to make a second prequel trilogy around the time he sold to Disney with his latest idea for the sequels.