I don't think what you have said here is wrong. I do think that judgements about social media are made from the point of view of people who hear about the evils of big (fast food) websites mostly second-hand while wrongly believing they don't participate in it.
My understanding is that this website was created was to make YC more famous among the kind of people who would post here. Posts are indexed by search engines and, after some period, undeletable. Like all social media - including all the way back to usenet, before the phrase existed - flaming, high-tensions, and consequences are non-negligible. I've seen someone write a post as an insider that got a reply from their CEO asking them not to do it. The sum of this is that YC's advertising is creating a platform for people to harm their careers.
Yet, despite knowing this, I continue to browse because I find value in the content that exceeds the dangers. I imagine others feel the same and hope that, by viewing HN under the same umbrella as Facebook etc., they might not view the negatives as fatal. At least not to the point of demanding other people leave their jobs.