Pretty much everyone figures out how to actually socialize, maintain relationships, have new relationships, improve them, and date at high school, MAYBE college at the latest. I'm 30, almost 31. Did I miss the boat on learning that and having a semblance of happiness in my life, and there's no going back.
I've tried it all. I've tried social hobbies, I've tried going out, I've tried putting myself out there. The basics of social skills elude me. I am, at best, a filler friend. I can't see myself being any more than that, and I think it's too late for me to get better.
I think I doomed myself to a life of loneliness, all because of the bad choices I made. The only possible hope I can have is maybe reincarnation is real and I can suck less in the next life.
anyone who did this would be my acquaintance, not a friend. When I make group plans everyone who hears about it directly is invited.
I don't want to totally invalidate your experience, because there are different levels of friends. I have some people that I get along well enough to invite to a small party and be happy to see them and hear what they've been up to. I have some people that I am happy to spend 8 hours with just me and them. A lot of your friends may very well be in this first group. Ideally this is a mutually-understood relationship. I also understand that I'm not close friends with these people, and I'm not offended when they do stuff without me (showing that I am not their close friend) just like they're not offended when I do stuff without them.
If you feel like all your friends are in this first group, there's probably a mismatch. Maybe your friends erroneously think you want to be loose friends; maybe you have a pattern of not showing up to events or not organizing hangouts of your own or accidentally sending some other signal. Maybe you're the one receiving signals they don't intend to send, and they'd happily come to something you organized or otherwise reciprocate.
The thing that I try to remember (and it's harder for men, we're poorly socialized and all seem to be bad at this) is that it takes two to tango. I should be organizing about half of all 1-on-1s, and about 1/n of n-person hangouts. If I want to deepen my friendships with people by seeing them more, I need to be taking the lead on more than "my share". If they reciprocate they'll match the effort.