It may be good for you to look back and see just how much those friendships and relationships have changed in those intervening years
I would also suggest that maybe you should change how you’re looking at these relationships, especially considering the time that’s elapsed between when you were in town vs. now. That would suggest that people have been stuck in place and have resisted any sort of personal growth or discovery in the intervening years. But that’s really different from “we have a lot of shared history together that made it easier for us to reconnect and get to know each other as we are now.” There’s nothing wrong with having new friendships with old friends after all.
Now, meeting new people is going to be an exercise in patience and measured steps. The estimated amount of time it takes to go from strangers to acquaintances, acquaintances to friends and friends to close friends is pretty steep and significant. Even if it’s not 100% accurate, it at least works as a rule of thumb and a reminder that friendships are built over time.
Unfortunately, time becomes an increasingly precious and rare resource as we get older. Part of the reason why it’s harder to make friends as an adult – leaving aside the cultural issues that make it harder for men to make and maintain friendships – is that life gets in the way. When we’re kids or in college, we’re in a place that’s almost custom built for making friends – we’re around people more or less all in the same stage of life for eight+ hours a day, five days a week.
Once we get older, suddenly we have obligations and responsibilities, we have work and overtime and chores and errands, relationships and children and so on
Grad school is its own level of hell when it comes to time management. A number of my friends who’ve gotten post-grad degrees have all agreed: grad school isn’t something you finish, it’s something you survive. For most, trying to maintain anything but the most important connections in your life is a nigh-impossibility between trying to juggle things like course work, TA workloads, research, dissertations and oh, casarse con alguien de otro paГs yeah, things like sleep and meals. Things that aren’t of screaming importance tend to fall by the wayside, if only because there’s only so many hours in the day.
This is why I don’t think people are lying to you or being clique-ish when they say they’re too busy. It’s that they already had those trips or parties on the schedule and – don’t take this the wrong way – you’re not at the level of friendship with them where they’re going to fight to find more flexibility in their social calendar. It’s not a measure of your worth as a person, just that you’re not there yet.
This is also why embracing weak ties becomes key and finding the areas where you can start putting in the time that helps bring you closer with folks. You may have to adjust your expectations at first, in part because some asks are just going to be too much. For a grad student, hanging out with someone new on the weekend may be just too hard to fit into one’s schedule, even if they really, really want to. It’s a lot easier to, say, start by making small talk before or after classes, or grab coffee and walk together to your next lecture or before office hours for the undergrads.
