> pervasive data trove from other services

I would believe that, although there has to be several alternate ways to measure a site popularity, Google Analytics are a huge part of a site ranking. Do users stay long on your website? Do they come back to the search results after that? Do they click through to "Pricing", then back to "Features"? If so, that must be the right answer.

Alternate example: I would bet that shops where Google Maps geolocalises a lot of customers have a higher-ranked website than similar websites where their physical venues are empty.