Romantic breakups are still fine, but do we ever recover from friendship breakups?

I (26/F) have been friends with this guy (28/M) since school times, we had a group, it fizzled eventually but we always stayed together. He had romantic feelings for me for a while, I was always upfront and honest about it being platonic from my end. When I had a breakup, he automatically expected that maybe it is his chance then despite of me being clear from the beginning.

We have been friends since we were kids, had our fair share of arguments, always made it work after that. My family knows him really well and his family knows me really well, you know the kind of friendship where you can randomly walk into each other's houses? We had that.

He got a girlfriend some years ago, she had a problem with me (rightfully so because this guy would hide things from her and make me look bad), the girl and I met and sorted things only to realize the version of stories he told us were so different. She still stayed with him and so did I, we tell ourselves this thing right, bachpan ka dost hai, we overlook things. Anyway, they broke-up few months later and the girl kept asking me for help, I tried my best to get them back together and she kept trying too, they eventually got back together.

There have been a few instances where there have been arguments between him and his girlfriend and my name got dragged and there have been arguments between me and him where her name got dragged in between. He and I had a few big arguments last year, he also spoiled my birthday (he knows I am a birthday person), I was supposed to move to US and I did, no contact from him(I was mad too because of the birthday thing), I tried to reach out eventually and we had major arguments. He blocked me everywhere, I tried to reach out to him many a times and get it resolved but apparently he doesn't want to.

I am currently on a vacation and it really broke my heart that I lost my school best friend, tried to reach out, says he's confused lol and needs more time(been more than a year since this is going on) and I was actually sobbing on the call, he didn't even make an effort to console me.

I have lost friends before but I always thought this phase of losing friends is only till you are 18-20 years old, who loses friends at this age? I mean, come on, we are adults, no matter what we can work things out, right? He made A LOT of mistakes, yes I got furious but I never left.

I have a close set of friends here but still, it hurts to lose him. We lived in the same vicinity, always kept meeting, trying new food joints, were each other's shoulder to cry on, we knew each other for almost 15 fucking years and now it is supposed to be all over because he is confused? I would really like to know a way to deal with this, romantic breakups are still bearable because you have your best friends by your side, what do you do when you lose your best friend?