If you're interested there are books on Oikophobia (there is one called Western Self-Contempt). It's a theory that societies generate a luxury class which loathes itself and attacks it's own history and culture.

This usually happens prior to a collapse in the example societies...

Yeah it's kind of hard to understand how someone can argue this without giving any examples. What would be an example of a civilization that's been destroyed by "modern liberal society and feminism"? "Modern" implies relatively recent, but I can't think of any civilizations that have collapsed recently. There are certainly people claiming that a collapse is imminent, but that's not a new thing either, and even if I were going to accept the premise that it will happen soon I still wouldn't agree with those as the most likely causes (and there isn't any objective way to know right now given that it hasn't happened yet).

I think the default mode is lack of population and getting outcompeted by pro-natal civilisations, like amish etc. You need to provide a reputable source for why is that not the case.