I think in a world without copyright, the ways that creative people earn a living would certainly change, but I'm not sure it would mean it would be impossible to be successful doing those things.

Musicians already earn a large portion of their income from things other than sales of their albums - whether it's touring / merch / advertising deals. All of that could exist in a world without copyright. The equivalent might not exist yet for movies, but in a world where movies were freely distributable, someone would find a way to still make it a business. Maybe the giant blockbusters would go away, but maybe that's an acceptable price to pay.