There's a conversation you can have with Klassje, after you read deeper into the story she tells you in your interview and realize that she's hiding things from you (and that Harry didn't notice because he's too attracted to her), where she talks about The Return. It's kept vague what The Return is, presumably so that you can fill in the blank (is the The Return of Communism? Monarchy? Independence?), but it's clear that it's a belief that the people in Revachol take seriously, and that gives them hope for the future.

The Return might be an upcoming coup being organized by Harry's boss, an RCM captain who's famous enough that Kim knows and looks up to him. This future event is revealed by having a high Espirit de Corps during the game's last conversation, and if Harry isn't fired from the force, the captain will be going down a list of who's going to be part of it and who will not. Harry will be part of the coup if the captain thinks that he'll "side with the people".

Socialist Infra-Materialism is real in the game's universe. You can learn from the Phasmid that the thoughts of people are creating a kind of climate change, which is proof positive that in Disco Elysium pure idealism can effect the physical realm - so why couldn't a large group of sufficiently motivated people bring better material conditions into reality by believing in them?

The final scene with the communist book club is the most hopeful scene in the game - a few people who are barely relevant, stacking matchboxes for an hour, into a shape that will almost certainly collapse. But for a few glorious moments, the boxes hold their physically impossible shape. That's what we in the writing community call a METAPHOR, and in this case it's for the seemingly impossible act of building socialism.