Where does the time come from to spend in that space?
It isn't that I lack sympathy for the problem, for goodness' sake. Indeed to a reasonable first approximation the only reason I bothered to comment is that "male loneliness" is of interest to me, enough so that a solution aimed at an irrelevant epiphenomenon of a different problem strikes me as worth objecting to on that basis.
That said, the formulation deserves some obloquy of its own, in that I think it likewise hits the nail squarely on the side by misattributing a problem of general social atomization. It isn't a "men problem" per se, so much as that - for various reasons related largely to social roles and experiences, and varying interests and approaches to same - men tend to make a good bellwether for some aspects of what I maintain is a broader social problem. Think "bedrotting" versus "gooncaving" - different codings, especially as respects men being defined as the sexually assertive gender, but the same basic social behavior. (Or asocial behavior, which is of course the crux of the problem.)
Note too that that isn't the "early 30s in Park Slope" problem. (I guess Boston has different trendoid neighborhoods. I don't care.) That, to reiterate, is the very natural shift of focus as young careers and young families both demand time and interest, as described in the OP. That's normal for this stage of life, and while it is very much worthwhile to try to maintain a broad circle, that really will not be effectively fostered by college-style social events no one is going to have the time to attend anyway - not when the same time could be spent more productively on social events that also build and reinforce bonds in the spheres which do and should absorb your interest at this time.