what is art not?
Short answer
Everything that excludes nothing.
Long answer
Art is not a fixed container. It began as ritual, became craft, then expression, then concept, then anything at all. When a category swallows everything whole, it loses its teeth. A word that excludes nothing describes nothing.
Art is not eternal either. The concept as we know it is roughly three hundred years old, a parenthesis in human making. Before that, cave painters weren't creating art. They were bargaining with the universe.
Perhaps the more honest question is: what does calling something art actually do? If the answer is nothing, then the word has retired. What remains is the making itself, which never needed the label to matter.