Okay first of all obligatory "generational labels are bullshit" disclaimer.
But I just noticed a lot of humour made by millennials as adults is very "cutesy" and "dad joke".
If anyone grew up in the 90s or 2000s, you know that we were the total opposite as kids. Seriously it wasn't long ago where the hight of our humour was homophobia and jokes about SA. We were the fucking horrible edgelord generation.
How did we go from being kids that would beat each other up for even looking at the colour pink, to the heckin' wholesome cat video generation?
Honestly I know we make fun of ourselves for the "HECKING POGGER PUPPERINO" shit, but honestly, it's a step up from the edgelord shit we grew up with.
This is, of course, ignoring that a lot of us didn't grow out of it and became your Ben Shapiro's and your Steven Crowders (I am so sorry Zoomers, we failed you hard)
From what I remember the Animation Show you're referencing was just straight absurdism. Like it had some of the violence of edgelord stuff, but the violence was usually used to heighten the absurdity, the incoherence, of the scene. The contrast between the light fluffy happy dancing cotton balls and one of them screaming because a literal ocean of blood is coming from it's butt.
Don Hertzefeldt animations are like the exact opposite of edginess, instead promoting an impression of earnestness through absurdism like you said. Op ought to check out Such a Beautiful Day and reflect.