The Philosophy of Pessimism: Retreat from the world or fight back?

Have you heard of the Philosophy of Pessimism? Have you heard of Rousseau, Leopardi, Schopenhauer, Nietzsche or Camus? Then you are aware of pessimism. This will not be a long prompt as I am only about a quarter of the way through Professor Joshua Foa Dienstag's book: "Pessimism" and I have also watched an interview with him on Substack by Massimo Pigliucci (who is a very nice guy and will converse with you on Substack). This is what I have learned so far about pessimism as a philosophy NOT as a psychological condition: as we are time bound and time aware beings, at some point, many say during the scientific revolution of the 15th -16th centuries and during the Enlightenment, we developed a belief in progress and "things are getting better." No one argues that we have not seen progress in the areas of technology, medicine and simply the ease of surviving. The pessimists argue that regardless of the advancements in those areas, we are not really progressing--a prime example: the 20th Century was the most brutal in history with two world wars costing over 50 to 60 million lives. We keep craving better lives and meaning but the world does not provide them. So, one key question the pessimists ask: should you simply retreat from the world or should we resist and keep striving. Schopenhauer advocated the former and Camus the latter: as he said "We must picture Sisyphus happy." In the current times, one certainly could be forgiven for saying the hell with it and withdraw. But maybe now is the time to resist even more intensely. Looking forward to your thoughts!