The answers to your questions are in the comment you replied to. Part of their love is music is sharing it with others. They also like to fantasize about becoming a full-time musician. Both of those things are less likely if there is 100x the current volume of music from unknowns.
It's not about validation, it's about expression and communicationw with other humans. That's one of the key beauties of art and it's being flooded away with artificial, empty content
Spotify does have a lot of AI generated music, yes. What is the purpose of your comment? Do you believe there is some filtering mechanism that is going to keep AI slop off of these platforms? Is that what we've seen happening with writing and art?
Good for you man, how will AI stop you? Are you writing songs for the pleasure of writing songs or for getting validation from other people?