Many ideological systems have been proposed, tried, and found lacking. Most of those people who still support these failed systems claim that the theories were poorly implemented, that if things were done properly there'd have been no suffering (no elevated risk of nuclear war, no purging of ethnic minorities, no setting up of police states, et cetera). Myself, I think that these people are confusing poor implementation with the inevitable gap between theory and practice. Theory never makes it out into the real world intact, without necessarily being deformed by preexisting human nature and by inherited cultural legacies. A successfully executed Year Zero might do that, maybe. But who in their right mind wants to take on the cost of that?