Why going to events alone feels harder than it is
The barrier is almost entirely anticipatory. You picture walking into a room where everyone else already knows each other, standing near the wall, leaving early and feeling worse than if you had just stayed home. That picture is vivid and convincing. It is also not accurate.
What actually happens in the imagined scenario is a compressed version of a social situation you have already navigated hundreds of times: arriving somewhere new without context and figuring it out. The anticipation compresses all of the discomfort into a single moment before it happens, which makes it feel worse than the reality. The moment you walk through the door, the scenario starts moving and your brain starts adapting. The thing you were dreading is usually over within five minutes, replaced by the actual event.
The other part of the anticipation is a form of social comparison that does not hold up under inspection. You assume that everyone else there came with people, that you are the only one who showed up alone, and that this is visible and notable. In San Francisco, where most people moved here for work and are still building their social circles, solo arrivals are considerably more common than that story suggests. You are probably not the only one.