I’ve been using Tachyons for the last few years and honestly the approach has left me very happy. I wrote a bit more about it in this Architecture Decision Record I wrote for the cljdoc project.
To me Tachyons brings the simplicity of functional programming to CSS.
There’s other alternatives such as TailwindCSS and BassCSS.
Disclaimer: I haven’t really investigated CSS-in-JS in seriousness.
Other posts mentioning Tachyons: