The horrors of World War I, Stalinism, Nazism, and atomic warfare produced the three canonical anti-utopias:

The transition from utopian hope to anti-utopian caution defined the 20th and 21st centuries. (PDF) The Ends of Utopia - Academia.edu

A world without Utopian thinking becomes stagnant and cynical; we lose the motivation to improve. However, a world that ignores Anti-Utopian warnings becomes dangerous, as it overlooks the unintended consequences of "progress."