Everything that is generated by AI is something old.
It's regurgitated from existing data.
No matter how well its obfuscated that remains true.
If image generation replaces human artists then the new/creative element eventually fades from art in its totality. Eventually all humanity and creativity is gone and we're left with AI's platonic reality for art.
It's like the dead internet theory but for art, eventually the automated slop will blot out anything human, and humans will make less art as a result.