So don't build a search engine: build a "rotten tomatoes for X" where the sources for each X are "the top N subreddits/communities/editorial-sites/forums for X".
For example, supplements: examine.com, reddit /r/supplements /r/nootropics (long tail ones), wikipedia, etc.
Then, final piece: make this aggregator site also a community (ala reddit/hn) where people vote on the results rankings, but also vote on how other people comment on them. Because you can lock down user accounts quite a bit (have high bar for registration with lots of verification for voting permissions), and you have a quality indictor for the users themselves (users voting on users), you may get much better results over time as the community sorts out who are legit and who isn't.
I'm not saying any system is immune to optimization/spam, but it feels like Reddit, HN, SO, Wikipedia at least prove that if you want good quality content, rely on a community. Why not extend the model to search itself?