Subjective though it may be, there are a lot of people who find black-on-white unpleasant to look at. I greatly prefer sites that don't use it, regardless of what they do with font and size. This could just be a case of conflicting preferences, but I don't think it has to be. Clear contrasts are achievable without insisting on #000/#FFF web design. - The most obvious improvement is simply keeping an eye on contrast.…
Shifting the background colour, slightly , tends to be vastly more readable than screwing with the foreground colour: https://codepen.io/dredmorbius/full/KpMqqB/ It also far more closely approaches the appearance of print on somewhat aged paper: https://archive.org/stream/commercialismjou00holtuoft#page/5...
Honestly, I don't think "too much contrast" is my biggest problem with black-on-white. It's the sea of #FFF that's unpleasant (with or without text), so something like HN's ~#EEE background feels way better to look at.