How the Web Became Unreadable
Kevin Marks

This new version has more contrast among text elements (both color and font size contrast) and major elements are easier to find. Blending details more to the background decreases initial cognitive load, then it is can be said it is worth user’s effort to find the detail after finding the general area of interest.

I do not think the point of the article is incorrect or the given example is perfect, actually I think it is terrible and it would be better if font-size contrast was preferred more. But this example of Google App Engine UI is not just fashion. One might argue the new version is better than the old version.