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?”
It isn’t surprising when you realize how many people Lucas had read that first script. Some very famous names. Brian Depalma, Stephen Spielberg, Francis Ford Coppola, and others. They all had input. That input is why the Toche station scenes were written (not Lucas’s original idea and they were only filmed because nothing else was ready to shoot). So the original film had a LOT of outside input. Bracket and Kasdan made the TESB script (the story was Lucas’s from day one) and Kasdan did the same for ROTJ. TESB is what it is because of the unique combination of talent. That was Lucas’s problem with the PT, he wrote and directed all of them himself. His flaws showed through. While AOTC had a credited writer with Lucas, it turned out the worst. He lacked the talented writers to bring his story to life and the right director to finish the job.
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.
I’m not sure we are in a position to see if it has a big picture or not. It took a while for fans to realize the big picture of the PT was the rise of Palpatine. It was a bit too subtle in the PT until they reached the end. I think and hope the ST will have a similar big picture in the final film that will tie the others in.