The Venice Biennale has been compromised and ruined by politics, suggests Laura Cumming. “Fifty festivals, a golden year, but no birthday celebrations. The Biennale has become so worried about its inflated status as the Grandest Show on Earth that it wouldn’t dream of congratulating itself in these desperate modern times. It is still a multinational market, of course, where droves of dealers tout their artists to rich collectors and curators on the look-out. But the real world presses in, and the director, Francesco Bonami, wrings his hands.”