Having read https://every-layout.dev (no affiliation), I cannot help but use CSS as a constraint system (ish).
My site for example, uses four "structural" elements - "the center", "the stack", "the box", and "the cluster".
That's maybe 50 lines of CSS controlling layout of the whole site, in concert with a proportional grid, much like how I do with print layouts. Except, with CSS combinators, flexbox, and semantic HTML. I don't use a "reset" CSS, nor do I use media queries.
Have a look-see. It's entirely hand-rolled CSS:
https://www.evalapply.org/static/css/style.css
nb. I'm mainly a devops/backend person. Any expert critique on said CSS is welcome. (Also site accessibility is a long-pending item... pointers there are welcome too.)