Any open voting system is going to be under serious SEO pressure.
That’s the real issue, Google has indirectly infected the web with junk sites optimized for it. Any new search engine now has a huge hurdle to sort through all the junk and if it succeeds the SEO industry is just going to target them.
A more robust approach is simply pay people to evaluate websites. Assuming it costs say 2$ per domain to either whitelist or block that’s ~300 million for the current web and you need to repeat that effort over time. Of course it’s a clear cost vs accuracy tradeoff. Delist sites that have copies and suddenly people will try to poison the well to delist competitors etc etc.
This is money spent by a search engine not money collected from websites. People don’t ever want to be sent to a domain parking landing page for example.
More abstractly SEO is inherently a problem for search engines. Algorithms have no inherent way to separate clusters of websites setup to fake relevance from actually relevant websites. Personally I would exclude Quora from all search results, but even getting to the point your trying to make that kind of assessment is extremely difficult in the modern web. Essentially the minimum threshold for usefulness has become quite high which is a problem as Google continues to degenerate into uselessness.
Reddit is an extreme example of group think. Try posting something pro-Trump (I mean, surely even that guy has a positive thing or two to be said about him) and you'll get banned in some subs. Or you may get banned simply because the mod doesn't like the fact that you don't toe the party line.
That just means that you have to curate the people allowed to vote. Otherwise, it would be rule by the obsessed and the search engine optimizers, and the junk sites will dominate the index.
I'm not convinced that Google's recursive AI algos aren't a functional equivalent. They let you vote by tracking your clicks.