The primary task of aesthetics is not to seek a theory but to elucidate the concept of art. Specifically, it is to describe the conditions under which we employ the concept correctly. Definition, reconstruction, patterns of analysis are out of place here since they distort and add nothing to our understanding of art. What, then, is the logic of "X is a work of art"?
As we actually use the concept, "Art" is both descriptive (like "chair") and evaluative (like "good"); i.e., we sometimes say, "This is a work of art," to describe something and we sometimes say it to evaluate something. Neither use surprises anyone.