I believe you underestimate the amount of good posts. There are many people posting personal stuff about their daily lives. There are many people posting art and stories they created. The original stuff is there. I tend to post on information I am interested in. I have used Wikipedia as a reference...cited of course. I try to draw in as many resources and links as I can, as I don't want to be discredited.
"What can be asserted without evidence can be dismissed without evidence" Hitchen's Razor
RE: The answer is ̶L̶o̶v̶e̶ Math (my own POV, what to do about plagiarism)