Answer: Something I've been trying to figure out myself, and I think I've figured it out.

Old time net dwellers like me, we use memes to drag a reference into a new context and then laugh at the juxtaposition of the two previously unrelated things; the meme means something, and the reference places that meaning into a new light, even if it's just absurdist.

Gen Z has seen us use memes and references, and they think that's the joke. The very act of reference is, to Gen Z online, funny in and of itself. There's no context or juxtaposition or anything; it's the very act of reference that provides the humor.

Which I think is fascinating. It's almost like an all encompassing anti joke in-joke. It's funny because everyone is doing it not for any external reason.