Well, he could have made better films of course. Collect some great minds around him, not just yes-men and yes-women. After all, he is the man who disliked ESB the most of all movies... while that is the best appreciated film of the entire saga. So somewhere in history Lucas kinda lost scope on what makes a movie work, or how a great collaboration makes a movie work as he became totally in control of his films.
Honestly, I can recommend any SW to read The Making of... books of the OT. They are excellent, honest. Especially TMO SW and TMO ESB show what a brilliant film maker Lucas was at the time. A true visionary, developing his story as he went along. (he once opened down the words 'Chosen One' for Luke... in ROTJ he claimed very clearly that Yoda and Palpatine were Force users of a different league, that they did NOT use lightsabers... etc etc).
It's during/after his divorce stuff changed in Lucas. You can se that in TMO ROTJ and TMO Indiana Jones. He admitted it himself, he was in a darker place. But his judgement changed as well for these movies. I guess in the Indy movies there was Spielberg as a powerful counterpart. But for ROTJ and everything after that, no strong side kick was there anymore. I fear ESB was the height of the collaboration of Lucas, Kurtz and Kasdan... and Kershner as well, of course. But that trio really made SW step into a momentarily grand universe of stories. Unfortunately cut short, literally in ROTJ.