Everyone has missed the most important aspect of search engines, from the point of view of their core function of information retrieval: they're the internet equivalent of a library index. Either you find a way to make information findable in a library without an index (how?!?) or you find a novel way to make a neutral search engine - one that provides as much value as Google but whose costs are paid in a different w…
They are also a spam filter. It's not just an index of whats relevant, but removal of what maliciously appears to be relevant at first glance.
We're talking about billions of pages and if not ranked (authority is a good hueristic), filtered (de-ranked), etc then good luck finding valuable information because everyone is gaming the systems to improve their ranking.
I think this is part of the reason you get a lot of fake news on social media. It's a constant stream of information (a new dimension of time has been added to the ranking, basically) that needs to be ranked and with humans in the loop, there's no way to do this very easily without filtering for noise and outright malicious content.