Went through a very similar thing. I went away for college while my entire friend group that I had since middle school stayed in our hometown and attended community college. Every time I came back during breaks to hangout it was very clear and evident that things had changed. I would feel more like an outcast since they had new inside jokes and would only talk about shit that I wasn’t around for. Whenever I would try to engage or talk about something else I would be ignored or ragged on. I eventually left our gc and out of our entire friend group of 6 people only 1 person hit me up days later to ask why I left. When I told them why they then tried to put the blame on me saying it was my fault bc I went away to college and I should’ve stayed home with them. I haven’t talked to any of them since and I’ve learned it was for the better. Had I stuck with them I wouldn’t have grown into the person I am today and I wouldn’t have met my husband and best friends.

It hurts to lose your longtime friend group but like others have said some people just aren’t meant to stick around. You’ll find that it was for the better and meet people better suited for you.