I wouldn’t say that downward trends in young people dating which can be judged by many consensus summary statistics ranging from a collapsing demographic pyramid to surveys of relationship satisfaction to condom sales to percentage of the population that self-reports as virgins well into adulthood is a “4chan talking point”. It probably gets talked about on 4chan, but it gets talked about in much more mainstream settings as well.

In places like South Korea the collapsing population is such an extreme crisis that the government gets involved very aggressively as a matter of long-term economic policy and national security.

The South Korean government doesn't seem to be doing much about misogyny. Until they get serious about that, a lot of young women are just going to opt out. The same applies to many other developed countries, to a lesser extent.