what has changed is the percentage of ppl living in big metropolitan regions where competition is higher and interactions plentiful and hence shallow making it more difficult to bond.

Small-town shop owner working sunup to sundown isn't a manchild, they're a hard-working professional. To my impression, this doesn't describe incels. Take their personality a few centuries back and you have the decent-looking but insufferable child whose parents can't merely be somewhat wealthy to overcome his misgivings.

Part of the problem is "the 1960s," a cultural waypoint for America, "were an exceptional period with respect to marriage behavior" [1]. In fact, between 1870 and 1960, we were at much higher fractions of the 45 to 54 age bracket of men who had never been married. Selection pressure was higher a century ago, not lower.

[1] https://users.pop.umn.edu/~ruggl001/Articles/Fitch_and_Ruggl...