I don't understand why it's being fought by left-leaning, many self-proclaimed communists that have been fighting for a world where we just hang out and make shitty art all day.

Isn't AI the only way we get to that? Who is gonna do actual important work otherwise?

The productivity gains would need to be shared by all to get that world, not owned by a couple for-profit entities.

Because (a) that vision of utopia is not party of any "self-proclaimed communist" philosophy that I've ever heard of, and (b) no one believes that's what's going to happen.

Instead the evidence of our own eyes tells us that AI seems to be worsening the K-shaped economy: a handful of Elon Musks will become trillionaires, a slightly larger number of engineers will become billionaires, and the rest of us will have fewer jobs and fewer prospects of upward mobility in a world where AI can do most entry-level work.