Makes me feel like there’s a potential for a CSS Zen Garden spin off: a collection of small CSS files that make basic HTML look nice. No classes, just styling on raw elements.

Indeed. That would be really awesome.

Oh, I discovered this too! I think it's called classless CSS and is actually a thing.

Here's a repo: https://github.com/dbohdan/classless-css

I wish the web had more simple CSS like this.

I use it for some of my personal sites. Partly because I’m not incredibly good at typography/layout and partly to save time.