You mean like having the idea for something and having someone better write and direct it. Lucas used to be a good idea generator, and with other directors and writers put out excellent collaborative work.
Other than that his reputation as a director can be called into question since he only directed 3 good films and 3 very bad turkeys 1 a film and the others videos that looked like games.
Even his reputation as a financer of other films, and as an executive producer or producer can be called into question.
What has he done of any merit film culture beyond the original star wars and indiana jones trilogies? And he directed only 1 of those.
Graffiti and Thx are seperate issues to me because they are more like extensions of his student film days.