I'm 22 and I realized something recently. This post is not intended to sound doompilled. If you're in your early 20s and you're struggling to make friends, the problem is not you and you shouldn't view it as some personal failure. People are just really busy with their lives. They're trying to focus on their education and career. Relationships and friendships are going to be really shallow at this age.
All my friends are from high school. I didn't meet anyone during my undergrad who was worth being friends with. I'm in grad school right now and it's not much different. Sure, I'm constantly surrounded by people with similar interests. But that doesn't mean anything when no one wants to do an activity with you that you would both be interested in because they simply don't have the time for anything.
My parents told me all their friends are either from high school or people who they met when they started their careers. So it's normal if you are either in your teens or your 30s when you make friends, and your 20s are going to be lonely but that gives you time to focus on yourself.
I'm going to be honest I don't like this stage in my life. But when I realized I'm not supposed to be having fun, I'm just supposed to be working hard, things got more tolerable for me. I'm going to reap the benefits of focusing on myself when I'm older, even if things suck right now. And I'll thank myself for not wasting time on men or one-sided friendships with pickmes.
My take on friendship:
Great friendships that last decades/a lifetime are so rare it doesn't matter when you form them, and you should form them whenever you can.
Most people are LV, so most people you meet at any age are not going to be your friends.