The flagged posts tool is frequently cluttered with Not an answer or Low quality flags on questions and answers from 2008 and 2009; I've recently counted 17 and 13 such flagged questions or answers out of the 50 randomly shown.
Stack Overflow is not the site it used to be; it doesn't seem productive to me to try to hold ancient posts to standards that did not yet exist. Some old answers should have been comments, but -- I think -- were made before comments were implemented.
So I propose adding a polite unicorn when a user flags an old post:
GEOCHET's answer is definitely lacking in description, but a -1 would probably do better than flagging.
These answers, and two more, (since deleted by Robert) might have been wrong, but they were at least suggesting libraries. 2D-only, rather than the 3D that the questioner requested. That's why they had negative votes. But they weren't comments. They weren't requests for more information. They were just wrong.
Incidentally, the question is a poll. Today we'd close and delete the entire question. But in 2009, it got 11 answers -- and remains open today.
I don't think I'd ever recommend marking a question as a duplicate of a code-golf question. (Which we mostly throw over the fence these days.) But the code golf question got 8 answers back in 2009, and it remains open today.
Those old questions and answers might not be perfection by today's standards. But they've been picked over quite a bit already and I think we've reached the point of diminishing returns. Our flagging and pruning efforts would probably be better spent on the contents generated in the last week.