If you are saying that hypothetical client knows a better song/artwork/code from worse, boy are you in for disappointment...
My point was that insane amounts of curated fully original works were required to get the output of these generative tools to the "occasionally impressive" level it is at now, and those original works exist precisely thanks to copyright. To say "oh we don't need copyright now" is to saw off the branch on which this hinges.
If you are into this stuff and want to see it become better you should rather promote copyright and differentiation of fully original works.