Professional artist here. The point of art for the human being is in the process of making it, not the end result. Artists enjoy making, trying, failing and learning. A robot can never enjoy what it does; it is just really good at cranking out more shit for a Capitalist consumer culture. What does it mean to be human? Religious ideologies notwithstanding, as far as anyone can actually tell there is no inherent meaning to the universe or to existence itself. We create our own meaning. Art for the human being is a response and reaction to this realization. We explore and seek to understand reality and our place in it by replicating it, bending it and reflecting it through our music, writing, drawing, sculpting and dance. We lose the plot when all we focus on is the end product and how it can be sold. In my day job I have to do whatever the client wants, but the art I make for me isn't about an end product it is about the journey of learning and getting better at what I like doing.

EDIT I'll add a couple of things. Our culture being what it is, of course artists hope to sell work , that is the system we live in. AIs will make that harder as they get better and actually figure out what the fuck hands look like.

I wouldn't call the above ethos "art for art's sake" it is art for human's sake.

If I were ever to use AI I would use it as a digital pharmaceutical. I would feed it only my art and see what the digital LSD could teach me about how weird I could get if I allowed myself to.