It's not about identity politics. It's not about self-deprecation. It's not even about if the material is particularly funny or not.
It's whether you're punching up or punching down.
If the purpose of Crap Towns is to punch up, speak to power, to point out the failures of Thatcherism, decreased social mobility through a perptuation of failing center-right politics thanks to an overly-powerful media and political class that is divorced from reality, the absurd dominance of PPE graduates within policy making, and on, and on, on... well, it's great satire.
If it's just to point at working class people and go "haha, their streets are dirty and they eat bad food", well... you're punching down, and it's rare that can work as comedy. It's just mean bullying.
So yes, you can write Crap Towns today, but it lands better if you draw the line from Thatcher through Major, Blair, Brown, Cameron, May, Johnson, Truss, Sunak and Starmer, and their acolytes - the PPE mafia on both sides of the House, and point out how their crappy politics has caused all this, not their victims.
Punching up is "look at them, ha ha ha"
Funnier comedy is "look at us, hahaha!"
Note that punching up is the same mechanism of humour as punching down. "look at people who are not like us, ha ha ha"
I always found the funnier things were not about punching up or down but were applicable to anyone. Restricting comedy to only be about punching up turns it into a political tool and not an art form that makes us feel better. Comedy that is only allowed if it sends a political message is firstly propaganda and then humour. It's why most modern comedy elicits a smile at best and no belly laughs any more. It can still be amusing but it has no universality.
The best comedy has truth about ourselves in it. Psychologically "punching up" is a rejection of these things in ourselves. Ideologically, "punching up" is a tactic reinforcing group identity coherence.
> It's whether you're punching up or punching down.
I disagree with the idea that one is "OK" and the other is "bad", "wrong" or, even worse, "problematic" (i.e., the bien-pensant's own "blasphemous"). It just makes one an eternal sacred cow, and the other the eternal punching bag, no matter either's virtues or vices.
And this, in fact, has already been the case for a long time. In the US, producer Dick Wolf's five Law & Order TV shows (and, now, his three Chicago shows) taught us over 30 years that the "wealthy CEO" or "high-powered corporate lawyer" is always guilty, and the large companies they own/work for are just as crooked. The only upscale demographic that is never the criminal is, strangely enough, the famous TV-show producer.