Dylan sings like Monk played piano and Hendrix played guitar. It's always been about phrasing, timing and emotion. It's never been about the less interesting aspects such as carrying a tune.
Daniel O'Connell can sing - he'd probably have made a better fist of this Christmas album as well ... in that sense. Or maybe Harry Secombe.
A slight objection to the latter suggestion is that Harry Secombe is dead. So, of course, is Daniel O'Connell, who has a rather striking statue at the southern end of Dublin's principal thoroughfare, now renamed in his honour. I didn't know the Liberator could sing, though. You live and learn.
Van Morrison can and could sing really well, Dylan never could sing and now he is 186 years old he really can't sing. This is no judgment on the quality of his songs.