I have also seen a good number of people who thought they were ugly but were not (Mainly talking about women as I can't judge men). I have seen women I thought were absolutely lovely but they thought they weren't. The sad part is, there was no convincing them otherwise as they assume you are simply being polite. We tend to judge ourselves harshly because we are often comparing ourselves to unrealistic expectations and online imagery. We then forgo character. For some reason that seems to no longer matter. Fuck someone having depth I just want to fap to them... That almost what it seems like at times.
Now, with that said, I know I am ugly. I literally have over 2000 rejections to prove it! I am the king of the wretched and undesirables! The rest of you are amateurs! ;)
In all seriousness, a lot of what you see online is not realistic. You don't have to be that to be desired, loved, appreciated or found to be beautiful. Beauty is a spectrum and everyone has their likes and dislikes. You don't have to be a 10 to be considered pretty and heck a 10 often is considered intimidating and most would be unhealthy jealous if they were in a relationship with that person. The problem is we have fallen prey to the online world, not the real world. Then add in online dating and the swipe culture that once again forgoes content and character... I for one actually enjoy these things.
Us depressed rarely get out and socialize and our future partners aren't going door to door to find us. I fell prey to this. For those that do get out, they often have issues like awkwardness that prevents healthy interaction. They assume they are undesired when in fact they may appear standoffish. These situations give the impression of being ugly or undesired.
Okay, I am rambling at this point and don't claim the above pertains to everyone, but it does to some.