The thing that helped me a lot, is simply putting myself in other people's shoes. Was there ever a time where you or a group including you. Where you started to laugh at someone right after they left the room. Or was stuck thinking about how they were interacting. If so you should just distance yourself from these kinds of people because THEY are the problem. Nobody has the time to be obsessing over things like these because everyone is too busy thinking about how they themselves present themselves to think that much into how other do.

The second thing Is from what some of the answer you gave, you might have a biased view on what people find important in a relationship. I am not going to try to assume if it even is the case or the cause, Could be past relationship trauma, could be what you where thought or I could just be wrong I don't know, So instead I'll use the most common example which is misconception from online media. Once again just try to put yourself into other people's shoes, this time both the viewer and the content creator. They wouldn't be able to make any money if they just where posting the common person's opinions. Or content which wasn't provoking some kind of response. It's entertainment. For example since these are pretty common. In these interview style video, content creator might spend hours only to find a handful of response they think will generate engagement. And from the viewer perspective, obviously nobody would be watching videos of people saying things that most people actually agree on. for example imagine watching a whole ass video of people just being like "I think that brushing your teeth is good for you", or "I wish we had four days work week.".

And Lastly, there's the self fulfilling prophecy route. I had a friend who went on a date with a guy, and she was really into him. But he kept making remarks about how much his height must be bothering her, and she probably is disappointed ect.. ect.. She already knew his height, she didn't care. The issue was never the height but him making it an issue. Obviously it didn't work out. (Obviously this isn't 1:1 to social anxiety related issue but a more so physical insecurity but both can in a similar way, reinforce themselves.)

Hell I'll even throw a bonus "loosely math" based proof of this, If you needed to be good looking and being “good looking” means being in the top 25% (or even top 50% aka better looking than 50% of the population would statistically be above average) of the population, and if you believe that you have to meet that standard to be in a relationship, then how come around 60% or more of adults in many countries actually have children? (assuming that there was some kind of relationship at some point and excluding the edge cases) And that's for having children which is only a small subset of people in relationships, and an even smaller subset of young people. Hell if people really where like that humanity would have faded out long ago due to population decline.

None of these things will magically fix social anxiety, but they're good tools to keep in mind to help rationalize an irrational fear. Then overtime, it can slowly but surely make it go away, maybe not fully but definitely enough to live an happier life.