It's subjective, it's vague, and sometimes unfair but that's the burden they have to bear. Defining the "quality" of a web page for a search has become as important a factor to web search as any other.
But "search quality" is a leaky abstraction like any other. When someone looks up a random phone number that just called them, they aren't looking for a blog post about it. They're looking for a very small amount of information.
Let's imagine we're determining the quality of a web page as a search result. Say we're looking for the combatants of the Second Boer War, so our query is "second boer war combatants". Now, if we had a page that listed only and exactly the names of those combatants, that would seem to be the "answer" we're looking for. But wait, isn't it better to see a page about the Second Boer War which has a lot of other information about the conflict? Or a page about the military history of the most notable combatant? Or even a table of major historical conflicts with their combatants?
Basically, although it would seem like a precise "answer page" is the best, there are a lot of other factors. The most popular kind of search results are often Wikipedia pages, so people seem to want that level of information on a subject. People sometimes search for something as a way to get to something else. The nature of the web indicates that pages with links to further information are more useful than those without them. And of course, as untrustworthy sites proliferate, the more well-compiled, organized and correlated information is on a page, the more reliable it is.
So ultimately, I feel like it's inevitable. As search has improved, Google has to make these kind of choices, in a quantifiable way, about the nature of a quality search result. And that ends up, in the tools-make-us stage of the web we're in, shaping the envelope of what web content is popular, even in some way acceptable. In turn, the web becomes easier for Google users to use by becoming easier for Google to index and search effectively.
But this is the more painful reality, as I also know. You get pushed out of the Google results not by sites with better information, not by sites that are more relevant, but by sites which seem like they can play the "Google game" better because they have the resources and profit motive to put together good metrics for the myriad signals that make you rise in the ranks.