Mother I think it's what I ultimately love about Bong Joon-ho films: he intersperses these seemingly grand tales of murder and betrayal with light, delicate touches of comedy, horror, gore, even some slight fantasy that only serve to further expose the messiness and mundanity of realistic, everyday life. It's the grey area, with no good, no evil, just being alive and playing the hand you're dealt, either learning to live with it or escape into ignorant bliss.
I think you said this better than I ever could. It's a common theme in all of his films I've seen, with Parasite being maybe the best example of it.
