I don't think you are wrong necessarily, but I think it presupposes that the main point is the Roleplaying, and the Game is secondary. I don't think that is necessarily true. I tend to think of the Game part being as important if not more important than the Roleplaying part. (Swap in "cooperative story generation" for "Roleplaying" as necessary.)
For me, it is always still a Game first -- we are there to play. So I agree that the specific systems should increase the fun of play, but I don't think they are necessarily in service to the Roleplaying aspect.