I don't think pro-copyright folks are claiming lack of copyright will prevent people from EVER creating art. It will just prevent a lot of people from creating

I don't think pro-copyright folks are claiming lack of copyright will prevent people from EVER creating art. It will just prevent a lot of people from creating GOOD art. It will be more difficult for solo artists to practice their art. And it will be almost impossible for multiple artists to practice their art (especially when they collaborate on something that can costs millions of dollars to produce) Enforcing copyright can inhibit creation of art that builds on other art. But they can only build on the other art if that art exists. Not having copyright means some of that art won't exist. Sure, you will have street musicians, and repertory theater, and people will still write books.