I find your statements hard to accept at face value. Does a "polymath" have infinite time to develop excellence in every conceivable discipline? How good was Benjamin Franklin at, say, composing sonatas?
Without any examples of his work it’s hard to believe that they are of any consequence. I don’t think anyone can just write a piece of music, but you don’t present a strong case that anything he wrote is even remotely worthwhile.
Hell, Bruce Willis has a band that’s released records. I just don’t see any reason to think they’re worth listening to over anyone else.