The best musicians play an instrument well. They also know that when they crate a song to set the tune to accommodate their voices. A musician like Bob Dylan is able to sound okay singing his own songs. Same with Billy Joel, who also has a limited range, but sings his range extremely well.
John Denver didn’t have a great voice but he did play the guitar well, and he wrote a lot of his own songs which were very popular. Bottom line you have to bring something to the table.