Reading all (or mostly all) of this, I go back to a basic truth. We sometimes accuse people of not being able to sing because the vocal quality doesn't agree; i.e., it's rough or sandpapery, reedy or nasal or like gargling marbles (Waits). But, what you find is that nearly all who have become famous, whether you like them or not, do have basic musicality and can carry a tune.

Go back as far as Louis Armstrong or Jack Teagarden; even Jimmy Durante. None were noted for clarity or beautiful tone, but all could carry a song with great feeling and style. People loved their singing. Rod Stewart and Dylan have both been excoriated for their vocalizing by some. Maybe it's an acquired taste, but SOMETHING made them hugely popular.