Well there’s another problem. I have never set anything to music.
Bernie Taupin can't either. But Elton John sets his poems to music. They've been a team since the beginning.
There are plenty of lyricists/poets who can't play music but have teamed up with musicians who can't write lyrics.
And most people that I've known who said they cannot sing simply don't allow themselves to try.
That said, some people truly cannot sing. My Dad could not sing, play an instrument, keep time etc.
He would put the "Dentist Office" channel on the radio and sort of whistle along with no regard for melody or timing whatsoever.
A fascinating and important influence on me musically since I found it impossible to emulate...