It is my perception that, at least in America and I suspect in many other places, competition pressure centered around places with strong "second place" (Job) opportunities combined with decades of civic mal-planning and treating symptoms (for some) rather than root causes (for all) have combined with a regressive tax/compensation structures to destroy the middle class and upward mobility.
There are not enough "first places" near jobs. The cost of those places and the demands of the jobs combine to sour the time, energy, and opportunity left for "third places" (#1). Areas and activities where idle time is spent when seeking connections to others. Those places, at least for me, also tend to have a high barrier to participation/entry and very poor discover-ability.
I theorize this might be related to the same issue described in another post, https://news.ycombinator.com/item?id=19902782 where "the old Internet" had many small venues, who's main reason for existence was not profit, but the benefit of their "members" (users). They were private, intimate, locations where fans of a given thing could gather and learn more about that thing and themselves; with small local histories that allowed for safer exploration.
A more stable place, where I had a real career I believed in, and a real home that I could start putting equity in to and around; a place where actual roots and structures and friends that would probably stay in the area also existed. That's what I feel we need to actually fight and win the battle against loneliness.