Confusing a bright, backlit monitor with a piece of paper is some pretty nasty 1990s logic.
I'm not sure about the original poster's statement that that site isn't accessible. I haven't tried applying a stylesheet from my browser to it, and I don't use anything to enhance contrast of text in web pages, as my vision is not impaired in that way. There's an argument to be made, though, that modern websites use coloring, layers, and a bunch of other things to achieve layouts, looks and feels to the extent that if you want to see content as it is presented, or to even find it readable or usable at all, you'll have a hard time with applying styles using your browser.
Believing that just because the web can be used differently to black-type-on-white-paper in a wide variety of ways means that every way of using it differently is virtuous is pretty mid-2000s web 2.0 logic. Contrast is useful, and its proven track record for rendering text is no mark of antediluvian shame, of irrelevance or datedness.
You seem to have read something in my comment that wasn't there.
FWIW, I discovered the Firefox plug-in Tranquility recently. It is sort of a light-weight Readability. Although it has far fewer tweaks available, it compensates by using much less resources. Readability was pretty much unusable on my low-spec laptop.
iReader for Chrome is a good Option. I tend to read most articles through it. Other browsers have their alternatives.
Do you have any suggestion for the CSS?