The reason the original trilogy worked so well despite the lack of planning and George’s amateurish writing skills was because it was a pretty simple story based on classical archetypes and tropes. On paper, the original movies look almost painfully safe and tropey, especially by today’s standards; but that’s exactly why they stood the test of time. It’s basically a cliché fantasy story with a sci-fi coat of paint. The original trilogy speaks to us on a basic, almost primal level; Luke’s path in those movies feels right and natural to us. LotR is similar in this regard; that story too will always be remembered due to its strong adherence to classical archetypes, which gives it an almost mythical quality.
Neither the Star Wars prequel trilogy nor the Disney sequels are like that. They are based on pure spectacle, and often try to be clever and subversive, and thus don’t really speak to the audience on a primal level. They feel way too ‘prosaic’, for lack of a better word. Controversially I think ASoIaF, while much better written than Star Wars, too suffers from this to some extent. I doubt people in a hundred years will remember ASoIaF to the same extent as they do LotR.