Something with such a broken rule that clearly hampers the game. The excuse that a defense would just sit back the whole game is silly. Sure some would try it... But when you look at other games and similar sitations, you see their logic is flawed and their only point is blind loyalty to the archaic purity of the sport. Offside ruins the flow of the game and hampers the sport. Imagine football, or basketball with a similar implementation of that rule.