First, most of the design work you are referring to comes from the print world, which has some differences from designing for a screen. Second, part of the reason that modernist styles were critically acclaimed is because they managed to pull off something very difficult. They violated conventions and still managed to create successful designs. This doesn't really change the fact that not using black and sticking with a more natural style is good general advice, just like the techniques of professional race car drivers don't really apply to the average driver.

Naturalism is a more forgiving guideline for people without a strong design background - it will help them produce better design work, partly because they have a baseline of comparison in their everyday environment.