Who is saying you/we are not high quality people? No one is saying that high quality people don't exist outside YC, just that YC accepts high quality people. You are committing the logical fallacy known as the fallacy of composition [0].
I believe this was the offending sentence fragment that implied the sentiment you say is not there: "the likes of which you are unlikely to meet in the regular world"
I read that as 'There's a higher probability of meeting high quality people in a location that actively concentrates them, then just randomly going through life.'
[0] https://en.wikipedia.org/wiki/Fallacy_of_composition