Imitation

I had a bit of a bone to pick with Quintilian's ideas on imitation.  I've always felt that imitation is fine for learning the ropes, and perhaps for being good enough to get by, but it won't be good enough to make any real difference or lasting impact.  Quintilian seems to think that imitation can lead to great things, rather than a copy of a copy of a copy.  While he says that "imitation is not sufficient of itself" (page 401), he is still advocating an ideology of "copy and do more" rather than "do something original", which bothers me.
I'm sure quite a number of lasting, important, influential works of art (whether in writing, painting, or anything else) have been created by artists/writers/etc when they decided to practice imitating another famous work and just change it a little, but not many come to mind.  Ulysses is on my shelf, but I haven't had a chance to read it yet, but I understand it is basically a retelling of Homer's Odyssey, set in then-present day Dublin, but I can't think of another work that I know of that was meant to be an imitation-plus and still had significance.
There are more movies and books made in this mindset today than out of it, but most of those are not going to be remembered in five years, much less fifty.
In my opinion, the works we remember and study after a long time has passed do more than simply "imitate plus" as Quintilian suggests, they radically redefine.  The Godfather wasn't made by Mario Puzo (the author) thinking "I'll write another mob book, but change it a little."  It was a complete re-imagining of what a story centered around people that were in a mob could look like.  And that is generally true for most works we remember and study today.