There's a philosophy called dialectics where opposites actually define one another. Atheism is a really good example of this IMO. Atheists usually define their beliefs as "no religion" but in practice they are anti-god, anti-religion. This means that even though religion has its own internal logic, being anti-religion has an opposite logic: what is good over here is bad over there. So it really ends up being that theism and atheism, through their contradictory traits, embody a single rational system.
But as many people have learned, through wrestling with these contradictions, we eventually reach a third stage where we just don't give a shit anymore, or maybe we develop some ways of grappling with metaphysical questions which religion is really good at but atheism basically just deny these problems even exist. I think that's why we often relate atheism as being childish, because a lot of people who are self aware and introspective will start out with a religious phase, then go through an atheist phase, and finally land in that secret third thing that is unique to the individual and their community.
I was recently reading a book about Hegel and early Marx, and the author Cyril Smith quoted one of Marx's letters saying something like, "atheists are like children trying to reassure a grownup that they don't believe in the bogeyman" do it seems like these "reddit atheists" have been on this same bullshit for at least the last 150 years
