And I'm saying that even if Lucas wrote the greatest story ever written but it makes no difference if Arndt and Abrams don't do a good job at translating it into a movie.
Alternatively, Lucas could write the worst story ever told and Arndt and Abrams could make something awesome out of it.
It's more on them than it is on Lucas. Lucas is just a guide in this...
The story for movies aren't written like novels, which is why the screenplay in movies matters quite a lot.