I'm in my early 40s, and my social life has been collapsing. I've always been weird, but haven't had trouble making at least some friendships most of my life. Like others in this thread, I never recovered after COVID.

It's interesting to think of this strictly in terms of aging. I had been thinking of it as strictly a "bowling alone" or "loneliness crisis" problem. Perhaps it's like a modern forest; the same old stressors can be too much when forests are dealing with pollution, parasites, ecosystem collapse, etc. ie, the old stressors are still there but everything is in a much weaker state.

Find a community!

People are still meeting other people. I have a good community with a great library and a park district. They offer many sports and other programs. Right now, I'm busy doing everything with my kid but intend to join some stuff on my own once he is more independent.

Science, book, and sports communities are amazing for meeting people. Then you just pick who you vibe with and see if they are open to hang out outside of the group setting.

The other person says "join a community", but those forms of community which are strong are so often unfriendly to weird people like us. For example, Southeast European cafe culture might still bring neighbours (well, at least the men) together daily over the decades, but someone unable to talk about football or engage in hyper-masculine banter is likely to feel left out and thought cringe.

We might look back on the early millennium, before Covid's devastating effect on groups meeting for special interests, as a golden age when even the weird could find their in-personal socializing niche. (Now someone might claim all is well in their neck of the words, but there are whole cities around the world where people are reporting the hobby events scene as nearly dead.)

If you don’t have kids by now your friends have moved on