Why such thin grey text? Why sacrifice readability as a matter of principle? What's wrong with black on white, like a regular f*cking book or newspaper?
Because paper is paper and screens are different. The white paper is slightly on the grey side compared to white on screen. And that hurts to look at for long.
Thin text is a personal preference that I made here. No principles there.
It becomes an accessibility problem, because the contrast is too low, and not all eyeballs are the same. Low contrast combined with a thin font makes it very difficult to read.
The problem isn't the colour choice for the font. The problem is with the colour choice of the background combined with the weight of the font and a thin-stroked sans font.