>but the apparent reason for many, many flags here is that the content is unoriginal.
Unoriginal to who? What's unoriginal to you might be original to someone else. So your justification for flagging only reinforces the groupthink argument even if you don't realize it.
Our branch of the thread seems to be drifting away from the original issue.
Whatever combination of user behaviors it is that HN's moderation promotes, it appeals to some people more than X, 8chan, gab, reddit, etc.
Perhaps some of the other sites contain the 20% of comments - with its pearls of contrarian wisdom - that HN flags. There is an audience of people (like me) to whom that absence doesn't matter.
I have no interest in wading through posts where there's no minimum bar for garbage. Some people do, and good for them: they can pan for gold on reddit, etc.
HN works well, as-is, for a certain segment of the public.
Unoriginal to who? What's unoriginal to you might be original to someone else. So your justification for flagging only reinforces the groupthink argument even if you don't realize it.