I dug through a ton of these for several days before finally deciding to just make my own...

All the lesser known ones tend to not be very extensible or themable beyond basic color changes, and they're a little too extreme about pure semantic HTML.

This guy has a really good roundup with last commit and GitHub stars info:

https://github.com/dbohdan/classless-css

Currently working on getting some issues with their test case ironed out to get mine (https://eternityforest.github.io/barrel.css/) included.