You should see what Cash did with NiN’s “Hurt”. F-ing amazing.
He can carry a tune, just not all tunes.
As for Rod Stewart - what does his being gay have to do with anything? As Steve Tyler once said, the number of gay people in the music industry is surprising.
Then he turns around and absolutely butcher's "Danny Boy".
There are some songs that once Cash does them, he own's them, but then there are exceptions.
Rod Stewart's music is gay; I have no idea about the man himself. That you would hold him up as an exemplar of anything "good" about music speaks volumes about your taste, though.