Guys like a Soderbergh or Welles have their fingerprints all over a film.
Conversely, if a director decides to be "hands off" regarding a lot of the stuff in the movie, as Kevin Smith admittably is, that is his decision and the movie's quality is affected by it (for better or worse).
I dunno, to me, ranking directors is basically a ranking of their filmographies. This is only adjusted if there a performance in a movie or something that heavily influences the quality. I dont know how "involved" in the process half the people on my list get, so its not really something I weigh in much.