If you have a musicial hearing, or whatever the term is , you'll use the major or the minor scale by the end somehow, no matter what.
BUT saying that basics and good hearing are enough, is just not true. Most of the musicians who didnt know any theory and wrote good music, learned hundreds of songs by hearing, so by that way maybe they didnt know how to name the scales, but they sure did know them, and used them. Also many of them had perfect pitch, like yngwie malmsteen, which of course made their life even easier...
I think that you dont have to learn all the theory, because you wont even use most of it, but you must learn the basics of it. In my opinion to say that you dont need theory at all is like saying that you dont need to learn how to bend strings or to slide....