When something is brought into the world through human intention, it has the possibility of being art. A human must stand next to it and say "This is mine."
The human role in the creation of art is non-negotiable.
Is a print of the Mona Lisa still art? Or is it worthless slop by virtue of having been created by a machine?
That's silly. There's lots of art with no known creator. Assuming the creator will never be known, it's functionally no different from art that has no creator.
We're already at a point where lots of "art" you look at might have had no human involvement; it could have been generated ad hoc by a web search or in response to the way you hesitated over something else in your feed (okay, maybe not already but certainly in the near future).
But we can't just say that anything that moves you is in a superposition of "art" and "not-art" until sufficient evidence emerges that it was created by a human.
Most people don't experience art through the "art historian" or "true art appreciator" lenses of "who made this and why". They just experience the thing for what it is.
2030's equivalent of Banksy could be a hacker who puts artistic images on major websites. It could then come out, years later, that it was all done by some AI agent. It doesn't matter if that's likely or not, it's obviously possible, and your definition can't just ignore it.