Why is a human-painting of an astronaut on a horse valuable now?
I view this as detangling composition from the mechanical skills of art production.
Perhaps this will make a new type of art job - AI wrangler - whose job is collaborating with AI to get a good composition, then the composition can be handed over to someone with the mechanical skills to render it in the real world, if humans making the brush strokes is important.
I'd imagine that if we gave these tools to a skilled painter to help in their compositional brainstorming process, they'd find many good ideas they'd like to incorporate into their works in a short period of time. But, I'm not a skilled painter, so could be wrong.