Alright, an oldcel's perspective, for what it's worth:
Third wave feminism (1990's) till today is the worst period, aggravated by Tinderwave in the 10's, especially in regards to young people. However, there is a larger picture in which the aforementioned are set, namely the fallout from Women's liberation/the Sexual revolution (late 1960's/early 70's till today). It's not that the loosening of sexual mores in itself were problematic. If patriarchy and traditionalism had still been in charge, that would merely have meant a lecherous decadence period of the kind that successful societies often encounter, like for instance in Rome during the Julian emperors. The problem lies enterely in the combination with women's liberation, as this tore down the protectionist barriers having previously prevented a return to the rules of the free market alphamale jungle, and female harem forming behavior, ultimately benefitting only Chad and depriving everyone else.
Such a development wasn't originally foreseen and only developed gradually. It takes time, generations even, for a female creature of habit to break entirely free from the ingrained behaviour and values of a patriarchal and monogomous past even if the moral state of the civilization is a virtual Gomorrah (like the western world in the late 70's/early 80's). During this period, I'd say there could even exist potential windows of opportunity for those who today are condemned to unrelenting Incelhood (there actually used to be something as compassionate femininity). Nevertheless, the train had been set in motion and the first stirrings of Inceldom syndrome are traceable to the 1970's (see for instance: The Elementary Particles, by Michel Hoellebecq).
One could even argue that the 80's indicated a marginal thawing period, thanks to the era's generally nostalgic/conservative and reactive anti-"60's" Zeitgeist. For instance, this was a time when in fact no high school girl of repute wanted to be identified with a worn out and embarrasingly out of fashion feminism. The 90's feminist and leftwing retro-wave, in combination with systematic political correctness, multiculturalism etc, stopped the 80's in its tracks however, and provided a decisive turn to the worse.
And on that road we've been on ever since, only augmented by certain instances of technological change.
Now, why this wall of text? At least I want to get through that history ought not to be viewed only in a linear, one-dimensional fashion, with only simple cycles following one another and a single temporal screen resolution. One has to view these things from several levels of height and acknowlegde that small cycles (Tinderwave) can be set into bigger cycles (third wave feminism), that are part of even larger ones (women's lib/sexual revolution), all explanations that by themselves are correct.
Thank you gentlemen for your time.