It's a sad fact that location comes into it as being in close proximity means you can go out together and share activities more often. I've kept up with a couple of classmates from secondary (in Surrey) and college but only because we're in contact through business. I suspect people I regard as true friends around where I live now (Brighton) will fall away were I to move away. Sad when it comes down to "ships passing in the night."

Nothing really to do with being not good enough. You're in a different league from most. I know roughly what you mean as I feel the same. Most people these days are self-possessed and victims of the instant gratification ethos. Most live in their smartphones; face to face is limited to workplaces. Many friendships are around the workplace as it's a socialising hub too. Otherwise it's special interest groups (like I do a few sessions of keep fit per week and pop out on occasion with others there. But I sense if I left a group (with promises to keep in touch) the contacts would soon tail off.) I dare say that in time you'll encounter friendships that endure longer. Let's at least hope for better times.