Especially Post-Covid it is made more worse, also from there is reason to believe more men are lonelier than ever since in general women have more friends than men when there is a friendship recession the men you had 2 or 1 friend will be alone. The lack of third places is another commonly cited reason this is especially true in the US where any place to hang out is optimized to get your money and get you the F*@# out. Additionally, there is also a class thing in the US people not working "corporate" jobs like those in retail/walmart hourly workers are doing overtime or tired to do other things. This is also responsible partly for the current "gender war" the lack of intermingling of men and women in groups if there are not men groups and women groups there will not be this mixed group thus it's not even an us vs them its me vs him , me vs her .... Birth rates are down things are going bad and now using falling birth rates as a reason they want to restrict the rights of women in the US, a deliberate calculated effort is underway with funding political lobbying, policy prescriptions etc the ultimate goal is control they don't give a damn about falling birth rates or gender relations or women or men for that matter.
I wonder how much of this also has to do with the aging population. It is harder to meet people when not in school, and well if it fades with time. The original connections notoriously fade more if the people involve have children due to the time commitment, and if they do end up in parents friend networks that may or may not replace it as an Alice knows Carol now from the PTA sort of thing.