You’re right but you’re also wrong. I know of social circles in middle age that have largely locked down. People have their routines and responsibilities and loved ones, and that’s that. They make little effort to clear space for new relationships. I also know other circles, also middle aged, where people have made it a priority to not do that. There is still flux and change in these circles.
Its a choice, basically. Not an easy one and there is no right or wrong here, but it’s not inevitable that midlife is characterised by social lockdown.
Location matters. In Silicon Valley, many people you meet are not locals, they come and they go. Like the tide. Other places this is different, like small towns where everyone knows everyone else. Some places people are more defensive, less friendly. Being an extrovert in a city where everyone is a visitor doesn’t help form lasting friendships and a faux pas in a small town can become a scarlet letter that follows you forever.
As others have noted, age matters. That’s well documented in the research from what I can tell but it’s also just a simple consequence of having marriages, raising children, etc… Coincidently that’s another set of life outcomes that are very impacted by place. Silicon Valley is known for that. “Man Jose” is not a great place to start a family, and career driven men from widely diverse ethnic and socio-cultural groups don’t form much of a community.
"Man Jose" is characterized by endless sprawl of modest single-family housing and is full of ethnic communities (South Asian, Chinese, Vietnamese) and families raising young children. It has more small neighborhood churches than almost anywhere else I have lived. Describing San Jose as a land of antisocial young men strikes me as frankly bizarre.
Its a choice, basically. Not an easy one and there is no right or wrong here, but it’s not inevitable that midlife is characterised by social lockdown.