Prettier Than Napoleon

Not to knock all modern art, but can anyone explain how this is objectively different from functionally equivalent interior decoration consisting of mounted purple canvas squares? What makes it art? That the walls are painted by an "artist?" They weren't; Rothko mixed the paint and chose the color and his assistants painted the canvases. It does not make a statement or evoke a feeling different from that evoked by identical interior decoration. There is a sharp division that the artistic establishment, as far as I can tell, seeks to maintain between crafts or decoration and "art." The Rothko Chapel highlights, for me at least, the arbitrariness of that line. Are we all artists now?