Batshit Monsterpiece Theater

Back before the days of the MCU and BVSDOJ when life was simple a little film came along and predicted everything that would follow after it. More relevant now than ever before, Mystery Men (1999) was widely regarded as a flop upon release. So why is everybody seems to have seen this film? What causes it to stick in our hearts and minds the way it does? And more importantly, is it any good?