the answer is no, quite obviously for me, since saying so implies that just by having such beliefs, one would be a good musician. So, not having spiritual beliefs does not say someone plays music badly.
Being a good musician, or good at anything, is something that stands completely on its own. How you got there is subjective, it will affect in which way you're good or in what, but it won't determine the quality as such.
It is quite legitimate to approach music pragmatically, not in the 'l'art pour l'art'-sense. Some make a huge philosophy about music and playing the instrument. Others don't (which i find very refreshing). But no matter how, quality is something there is no formula for.