Been thinking about this since I've been playing Rain World. I feel that Rain World is solidly within the genre. There are definitely video essays out there about it being about existing in an ecosystem or whatever. Pathologic is another obvious one. The original Dark Souls is probably paradigmatic of this category.
What traits define this category? I think:
- Difficult, you struggle to make progress
- Inscrutable narrative motivation
- Hidden depth to the world that can be teased out through intensive study
- Possible to find it fun, but much likelier to just bounce off (and watch the video essay instead!)
Is this a valid category?
There are, I think, exactly two that haven't been mentioned yet: Pathologic 1 and Immortality (2022), the former for being conceptually fascinating while borderline unplayable and then the much truer example, maybe the only true example here, Immortality for being a convoluted knot of kind of a plot held together by gameplay consisting of sifting endlessly through footage and nothing else.