But is it art?

This is a sign outside the Dean Gallery in Edinburgh and so I assume it must be. Thinking of having something similar on my kitchen door.
Trip to the modern art and Dean gallery with a couple of friends today. Some very strange stuff. I'm usually fairly open minded but wasn't too sure why a room decorated with black wall paper patterned in phalluses with some metal drains and a plinth holding a bag of old donuts constituted art. Similarly a room filled with plaster casts taken by a woman and her partner of patterns made when they peed in snow. Baffling.