That was me when I wanted a heavy metal song about a common office annoyance and prompted Suno to create "Per My Last Email":
People regularly compose symphonies that aren't playable by any orchestra. In the worst case they have passages not playable on the actual instruments because the range is beyond the instruments' range. If a human can't play it or it can't even be played in theory on the instrument, then is it really self expression? What is being expressed, exactly?
This is getting to the core of what music is, and isn't - and part of what music is is an expression of mastery of craft.
Would you still call it an expression of yourself if you paid an artist to write a song for you around an idea you had? I don’t think most people would generally refer to it as “expressing themselves” when they commission another artist.