I used to have an LP, "Andre Previn Plays Fats Waller." It was (as I remember) a good album more Previn than Waller. That's the nature of Fats Waller--he wrote a multitude of songs that others could record and add their own stamp to.
But that's not the nature of Art Tatum. It's hard to imagine an "Andre Previn [or anyone else] Plays Art Tatum" album. Only Art Tatum could play Art Tatum.
That's what I think Fats Waller meant by describing Art Tatum as God (and what your poem opened up for me): religious people strive to be like God, but they know they can never replace God; there is only one God.
There are a few other "gods" like this (Charlie Parker, John Coltrane, Miles Davis, Bill Evans....) and we should be grateful for their unique contributions that enrich our lives.