With the vast amount of books and user data that Goodreads holds, it has the potential to create an algorithm so exact that it would be unstoppable, and it is hard to imagine anyone objecting to their data being used for such a purpose. Instead, it has stagnated: Amazon holds on to an effective monopoly on the discussion of new books – Goodreads is almost 40 times the size of the next biggest community, LibraryThing, which is also 40 per cent owned by Amazon – and it appears to be doing very little with it.
This is the dirty secret of Amazon: they suck at search because they don't have to not suck at search. They're going to sell you a something, and as the seller, it doesn't have to be the right something. Ideally it's the something that makes them the most money, not the something that serves your purpose. So you look for something and Amazon will give you a hierarchical list of things that make them money. If you buy something that they don't own outright, they add that to the ranking of "things Amazon should rip off so they can make more money." Meanwhile if you grow frustrated with Amazon's search, you'll do what everyone does, which is google stuff, which will also bring up Amazon links. Quality search serves you, not Amazon.
They make it really easy for sellers. The Twilight series has a number of descriptors. If you want to show up when searching "books like twilight" you use those descriptors. You use the same cover art. And the book doesn't even have to be good, it just has to come up. Maybe you sort by reviews, but probably not: ReviewMeta had never seen Amazon's top hit for "books like twilight" before in its life, despite a thousand 5 star reviews (which ReviewMeta then decided were 30% fake). Meanwhile if you use Amazon's publishing you have ready access to a couple dozen lists full of groups you can give free copies to in exchange for reviews, which will be on GoodReads, for a fee of course.
The model works for more than just books. Amazon at this point is a front-end for drop-shippers fronting AliExpress garbage under a dozen different names. Amazon sucks at search so entrepreneurs sell low-grade crap on the ratio. There is no aspect of the model that rewards quality, you just have to outrun the bad reviews... and a thousand three star reviews are more compelling than a dozen five star reviews.