I think, OP, you have to acknowledge that those posting are more likely to suffer from depression because by definition they have got to a point where they can't see the woods for the trees, and are reaching out for ideas/ ways to deal with their situation.
For every person on here with a long list of awful things happening, and feeling frozen, bleak, lost, the will be many with a similar list of woes who are just "getting on with it"
Whether it is genetic predisposition, or a lack of coping skills, there are plenty of people who get seriously depressed in situations that others would not find the same.
Therefore, it is worth mentioning, ticking off the list, because you could try any amount of brisk walks, chucking out oafish partners, leaving stressful jobs, when it would actually be useful to know whether your RESPONSE to the the situation is within the normal range, or more severe.
Equally, I think there have always been Many people with narcissism, depression, ASD etc, who have not been diagnosed as such, and therefore have had miserable lives/ miserable loved ones. It's a bit like saying, " well we didn't have seat belts and we were fine ". Yes, because you're not the ones that died.
Just because it doesn't seem relevant to you, doesn't mean it's not relevant, and life changing, to get a clue to why life might be extra hard shit.