I don't know...
When I finished school in Germany, and social service, and wanted to study, I decided to move away from my family. I wanted to be more independent. And so a person I knew well, who was living in another pretty large city, told me, that some close friends of hers share a flat, and there is space for one more. So I thought "what the heck" and moved in. Sometimes that was a bit stressful, but all in all it was nice, and I made friends that way. It's easier than when you live alone.
Earlier this year, after sharing that flat for 10 years, I moved out, and into my own flat. I moved into another part of town, closer to other people I know, and now I see them more often.
I sometimes do feel lonely, alienated, and wonder if I have any true friends. But from a logical point of view, I have them.
In the end, I think it depends on where you live. People in tiny villages of course have a harder time than those living in larger cities. But thanks to the internet, making friends is now easier too.
I have people who want me to join them on activities, who are happy when I'm there, and so on. But I've noone whom I could just phone and say "I feel ****ty, where are you? I need to talk".