I don't think ranking based on upvotes, downvotes, or other forms of engagement is necessarily terrible, but it's certainly nothing to do with "market value", a

I don't think ranking based on upvotes, downvotes, or other forms of engagement is necessarily terrible, but it's certainly nothing to do with "market value", and misleading to suggest that it is. If you want to create a way of ranking websites and call it "SocialRank", or "EngagementRank", that's fine, although see below. However, users would have to be aware of the severe limitations. You've already highlighted some of the problems with social content: it's often spammy, low effort, clickbait, poorly written, misleading, or outright false. The quality of the search engine and ranking algorithm is going to be judged by the quality of the results it returns, which I'd imagine will be pretty trashy in this case.