What's so bad about finding the meaning of the story as he went along? He says that he set out to create a modern myth, but when he purposely set out with the intention of covering all the Mythological bases, he had all kinds of trouble. But when he just focussed on the characters, and started letting the story unfold, he noticed that many of the components of Myth appeared organically without his direct intention.

It's not like any of you guys were born with a 6 film saga all worked out in your head, why can't Lucas make it up like everyone else in the movie making industry?

At least he does a good job at it.