The prequal trilogy is just poorly made down to a very fundamental level. When Lucas started out he had limitations and lot of other people to keep him grounded. After achieving much success and taking most of the credit for himself, he was unopposed and could do whatever he wanted. In 1983 he divorced his wife Marcia, who had edited every feature film he'd ever put out, and had done a great deal to keep his feet on the ground. Then CGI was perfected and he was able to put any retarded idea he wanted on the screen.
Lucas is best when constrained by other people, which isn't going to happen anymore thanks to his ego. The man hasn't made a good movie since 1995, and probably never will again.