However - Lucas DID basically whip up Empire Strikes Back’s story/structure more or less all by himself once Brackett was gone. Kasdan contributed heavily, yes, but by the time he came on the bones of the thing were firmly in place. But on the other hand: The most famous twist of all time, probably, and the one that basically doomed Star Wars to forever be taken way more seriously than it ever really needed to, and trained its biggest fans to expect twists and turns and huge surprises in every chapter despite the fact it’s ALWAYS been a straightforward fairy-tale other than THAT ONE TIME… that twist was basically pulled out of his backside at the last second before shooting started. It wasn’t a deeply considered, thought-out idea. It was just a hand grenade tossed at the end of the story to create one hell of a cliffhanger for the next chapter.
Right, I think Lucas is a pretty good “big picture” guy, but when it comes to screenwriting and directing most of his work comes off sooooo flat. That’s why Star Wars 1977 is so perplexing. It’s the exception to the rule. It’s funny and emotional and when you watch it you think, “this guy wrote and directed the prequels?”
One of the biggest problems with the ST is that there was no “big picture” going into it. And it’s definitely been a detriment to the series. No matter how much you like TFA and TLJ as individual films (I think they work pretty well separately), there is very little narrative continuity between the two. And the way TLJ ended, there’s unlikely to be much narrative continuity with Episode IX either. The ST desperately needed a “big picture”, but I’m not so sure George Lucas would have been the right man to do it.