The thing a lot of people do not understand is that social isolation is self-reinforcing and so is social connectedness. Making new friends can either be anything from the easiest thing in the world to nearly impossible based on how many friends you already have.
Like I've gone through some pretty serious socially isolated spells in my life, and those first steps of building or rebuilding a network are always the hardest and most prone to failure. It's really easy to think that lonely people are lazy or unmotivated for not "building community" as fast as you can, but the relationship of effort to progress is completely different.
Are you still allowed to have boundaries about connecting with individual people who make you uncomfortable? Absolutely of course you are. But declaring all socially isolated people to be beneath you is gross, as is encouraging others to do the same.