True, but keep in mind that just because these hidden services' true identities aren't known, doesn't mean they can't have a reputation.

If this search engine becomes popular among Tor users for example, and you follow a few news sites which focus on stories related to the dark web, you'll end up in basically the same situation as you are now with Google. (With the search engine losing the trust of its users if it starts behaving maliciously.) Same goes for other hidden services.