You’re right. But at the same time that quality seems to decline or at least stagnate. I think they face the hard problem of an decreasing signal to noise ratio.
Ranking is definitely easier when you also provide and moderate the content. That implies the technical solutions might differ qualitatively.
Google indexed the same sites as Altavista, but Google Page Rank made the right sites bubble to the top and made Sergey and Larry billionaires...