Are you a Songwriter who has ever said this? I’ve heard a lot of this over the years.
It’s puzzling. Why not train your voice? If you are writing for singers, you need to know how singers (I mean real, not digitally-enhanced) sing and how to compose a terrific song.
Why not work with a singing teacher to build your voice and your presentation skills so that you can sell your songs? Instrumentalists usually study and train, why would you not train your instrument?
Hum. It is time to return to respect for the craft of singing.