You are arguing in theoreticals, so you should not be surprised if your answers are hypotheticals.

In reality most art is done because the artist has something to say, and the money they get from it is only motivating in as much as it enables the artist to do more art. So I would guess in a world without copyright protection we would just find other ways to pay artists and a very similar amount of art would be produced.

You can see an example of this e.g. in Iceland where the market is way to small for art aimed at the domestic market to make enough money solely by selling it (possible with music; rare with books; not possible with movies). Instead the state has an extensive “artist salary“ program, which pays artist regardless of how well the art they produce sells. Unsurprisingly Iceland produces a lot of art and has many working artists.