If instead you define art as the communication of things that can't be fully expressed by direct sterile language, that's something I can get behind. Going that route, I think that getting AI to create real art has some pretty clear challenges, but there are also ways whers I could see it being better than humans.
Depending on how the AI learns and analyzes it has a chance to have a unique perspective on human communication. From there, it can find new and innovative ways of identifying gaps between primal human experiences and sterile human communication - and with a unique understanding of human communication could come up with fascinating ways of bridging those gaps.
This is all spitballing, but I think AI could eventually be the main new frontier in art.