Lots of sweeping conclusions in the article and not much support. I'd bet this trend has been going on at least 30 years and has built up gradually as more and more manufacturing jobs that provided a middle class living were moved out of the US, or simply lost to cheap imports as tariffs were reduced or eliminated.
Not buying the author's "not for lack of jobs" claim. There probably are unfilled jobs in some limited areas, but nothing remotely approaching the drop of several million in the workforce participation rate.
That is because lack of jobs is a relative term, and here it is used as a binary, jobs or no jobs. The jobs that exist are not attracting people who are unmarried or divorced, and can go by on the margins of the society.