I got some idea spooking around in my head for a while on how to best do a setting a bit alike some ravenloft domains, like Falcnovia with its oppressive regime or the one which map is basically 19th century industrialization London (cannot recall the name of this one atm it's got some Jack the Ripper theme I think).
What I imagine is something extremely gloomy, literally dark, maybe foggy but not always, but when not, the sky is clouded also with smog eventually. It should be a populated area on the one hand otoh many houses should be empty or inhabited by something else than the normal folks. The normal people would only leave their homes if they absolutely have to.
Basic things like water and food supply should still work somehow though, but I have no good idea on how to make this logically consistent, because this would require rural areas providing these goods.
While the rural areas could be as gloomy and dark, having lonely farm houses strewn about, there would have to be some market or traffic of goods in larger quantities. I do not know how to resolve that.
That's where darksun really shines, it is thoroughly consistent and still gives that postapocalytic feel.