I've made more new friends in the last 3 years since I moved to SF than, I'd honestly say, my previous decade living in NYC. I'm 37 now and feel like I have more of a community than in college.
I think the key to finding real friends and friendships is to be in a place where you're going to be surrounded by the kind of people you WANT to be friends with. It doesn't involve over-thinking or forcing it: I'm a 30-something dude who loves tech and being outside. There are a LOT of people like that in SF. I figured that out within a week of visiting 3 years ago, so I moved here.
Say what you will about monoculture, but it sure made it easy and fun to find a community of people I liked (and vice versa).