I feel you man I haven't seen my best friend from high school in years. We had a lot of plans and dreams, we were going to be hanging out when we were fifty. Just drifted apart and became different people I guess.
We still get along really well whenever we see each other but our lives are just so different now.
I have new friends and stuff now, and I'm currently doing better in general than I ever was back then.
But god damn dudes, I've never had another friendship like that. Even romantic relationships don't have that same fulfillment as having a number one best bro around.