Someone else has probably said it, but lucas needs someone there to guide him. The first movies he had a lot of help, and he wasn't allowed to do as he pleased. Han Solo was going to be an alien for ****s sake, lol. For the prequels he needed someone there to slap him when he thought up jar-jar, but the studios let him go wild since he was/still is so successful.
I enjoyed the prequels, except for the first one. It was just straight up garbage.