CSSdev has been the bread and butter of my last 10 years of work, and I still have the feeling that CSS as a language is never designed, just expanded.
A series of modules that are bolted on top of existing properties without actually improving on them, simply "well, here's another way of doing the same thing" often in ways contradicting each other (see the way the box model works in "display" vs "flex" layout) or just slightly diverging in ways that make extremely hard to debug them (e.g. how gap works in "flex" vs "grid" layouts[1]).
The awkward point-based cascading system means that once a layout is written it's basically frozen, unless you use some convoluted native or js-based encapsulation systems which once in a while gets leaky and, who knows, your component topbar font-weight mysteriously goes from "thin" to "extrabold" or your mobile menu appears even on your desktop breakpoints.