I usually flag comments quibbling about website style, but this one is specifically about web typography, and the first thing you should learn in typography is

I usually flag comments quibbling about website style, but this one is specifically about web typography, and the first thing you should learn in typography is choosing the right font (which, to be clear, isn’t a point discussed in TFA). No one will care about how you indent paragraphs and lists if they can’t even read the text without great difficulty. If people reach for reader mode, all your custom typography is lost. I also find some of the advice in TFA like vertical rhythm (“one important aspect to get right”, I quote) dubious for web typography. Unless you’re using multi-column layout, there are no pages to line up on the web.