Suspect the types of people most likely to write these high quality posts don't stick around forever because they find something else to do sooner or later. Motivation is high when everything is new, you are curious to understand what is going on and there is still some abstract hope that you either discover some kind of way out of this hell or that society would switch its perspective if you just find the right words or data or arguments. By now many of the people still around simply are the kind of people with nowhere else to go, the complete social outcasts.
If you want to keep high effort posters around, accumulating status in the community must pay off in some way, which is usually a natural consequence of gaining and sustaining high enough user numbers. You want there to be enough people to allow for a constant stream of content, for some financial opportunities, for minor internet fame and so on.
The hyper offensive tone probably also plays a role, no one wants to be associated with this site under his real name. Which strongly limits how engaged and connected people can get. And it creates an intolerable barrier to entry for >95% of people right from the start. For the ones that stay, being that unfiltered and uncontrolled in their use of language might also be one factor as to why they can't find other communities to integrate with, not even online.
Same with age. The younger the user, the harder it would be for him to create worthwhile content (less time for (self-)education, less life experience, less time spend as an adult interacting with other adults) but the more free time he'd have to waste on here. More overboiling emotions, still trying to find his identity and still trying out perspectives and ways of life. Less nuance, less self-reflection. On average. One would hope.
No sure what else. Although this one is also undoubtably part of it.
People just have ran out of things to say