Yeah, whenever I read this it makes me cackle like a hyena;
a) because it's usually a newb (no offense to newbs) and
b) because it's an example of someone who doesn't know anything about music and has no plans to.
Tell Beethoven, John Williams, Alfred Newman, Wagner, Mozart, Haydn, Scriabin, Schoenberg, Bartok, the Bachs, Mahler, Bruckner, DeBussy....dozens more composers considered the greatest in all history that. They all knew theory inside and out. Why would anyone listen to that sentiment from you and discard the facts?
Seriously consider dropping that little axiom if you actually plan on doing something in music, my friend.
All that said, I do think being overly concerned about theory and thereby letting it get in your way is possible (to set the record completely straight).
What makes one person know more about music than another person? enlighten me, please.