Masculinity isn't just being devalued, its being outright attacked. Its considered "toxic" now. Men don't know how to be masculine because they are taught that being masculine is wrong, or "evil". That masculinity is dangerous. That men are dangerous. That they are all violent, wannabe rapists that oppress women and (if their white) minorities just by existing. In that environment, how many real men do you think would continue to carry the standard of masculinity. Add in the epidemic of fatherless homes, leading to a generation of men who are being raised by women who literally cannot teach them how to be men, and you've got one huge recipe for disaster.
This is the problem with conservative thought. Conservative thought is more about trying to the general masses. For one thing, masculinity should never be about being popular or liked. If masculinity is about those things than it's in trouble. Some people have this 1950s ideal of masculinity which pretty surface level.
Blame soft living. In an environment where everyone has enough to eat, Nature wants us acting hedonistically, not fighting over food and resources. Naked aggression then becomes demonized while status and power are doled out by other means, and usually to people who are best at living within the new paradigm. Traditional gender roles of all stripes get scrapped in times of plenty - this not only includes men's status as protector but his status as provider as well. If a woman can earn her own income by working a cushy job indoors, she doesn't need a strapping young man to take care of her. This is why there are so many incels around; in times past, even the most awkward of spergatroids could've netted themselves a wife just by buckling down and working a decent job, because most women had no choice but to marry if they wanted an income. Example: Mr Collins from Pride and Prejudice, who is utter girl repellent in the novel, but manages to snag a plain but adequate woman as his spouse because he's set to inherit a rich estate.
For the record, I'm a woman who's happy I don't have to marry an Urkel with a good job to keep from living in penury, but I can see that the equality that women's lib promised to bring hasn't quite come about. I'm not happy that men are considered rapists by default just because policy makers decided that the best way to undo sexism against women was to slingshot so far in the other direction that society is now sexist against men.
That's funny you mentioned Pride & Prejudice, which was set in 1801. I read Buddenbrooks by Thomas Man that chronicles the life of a upper middle class family from the years of 1835 to 1877 in Northern Germany. Antonie was able to marry and divorce two times during the novel. Her father sanction the divorce for the first marriage be cause the first guy was could not live up to Hanseatic bourgeoisie norms. Though, the second guy, from Southern Germany which was more Catholic thus laid back in regards to business, was wealthy and a good provider was divorced due to his laziness.