Many years ago I did a very deep dive into the CSS specs as I was researching for a new implementation and it struck me as well designed for its purpose of separating style from the semantics of markup.
When it comes down to it, making a great looking and maintainable page is just as much work and planning as building a good backend codebase. Neither one just happens.
Lots of "real" devs treat HTML with similar "I don't need to really learn this toy markup" kind of attitude. The worst CSS issues I've ever had to deal with were often caused by horrible markup that was impossible to consistently style.
Basic stuff like how to make a good `<form>`. Putting `<label>` elements next to your `<input>` elements, or making sure the `for` and `ID` attributes are set. Hell, even using `<label>` instead of some `<span>` they threw a bunch of random framework classes on.