@volemaulder: I feel you're leaning heavily on one side and perhaps missing some of the forest for the trees.
When I mean bleak and miserable, I mean any game where the overall tone and mood is dire. There's a lot of washed-out colors, angry faces, and most people--barring the protagonist and/or their entourage--are either suspicious or antagonistic.
Fair enough, you're not wrong to observe this. I am quite tired of this myself, if I'm being honest, although I wouldn't usually think of such games as so-called mature ones, necessarily. I guess, technically, as someone pointed out previously, from a ratings perspective, they are, due to certain imagery and content (e.g. violence, language etc), but that's never really been the focus of this topic, at least I don't think so.
@pezen is also on point two posts above, well said.