I look down on celebrations/events because I was barely invited to any as a kid

Or at least I think I look down on celebrations. Whenever there is an event or celebration of some sort and people come together to have a good time (eg a fandom’s anniversary), I immediately turn sour and just wish the day could hurry up so the event would be over and out of my head, so I don’t have to see people being jolly and posting about it on their socials and having a good time together. I really don’t want to sound like that guy but I feel any potential joy I could have in celebrations have been sucked dry to the point I just view it and the people celebrating as all cringe. Like instead of thinking of the joy of coming together as eg. a fandom to celebrate, the only things running in my mind is “pathetic” or “pff, I don’t care, can’t wait to see all the cringey mainstream posts”

However when it comes to family dinners/birthdays, I seem to not mind at all. This brings me to another question, do I loathe celebrations because it is not about me? Or rather, because I’m not closely related to the person or thing being celebrated?

Am I just a miserable person?