If you're a common web developer or even when you just started, you'd probably already have heard about the terms
CSS. Both are meant for different purposes and both (most of the time) are necessary for delivering the product.
However, many (web) developers have a prefer to pay more attention to one of the two sides.
CSS in that case, a stylesheet language, it is not possible to implement features like we just mentioned. However that doesn't mean
CSS is not important or even complex. The opposite is true! Many software developers who started once with their career as programmer, chose for backend programming because of the complexity of
CSS. You have to think about a lot of things by styling with
CSS. Think of responsive web design, mixins, spacing, positioning etc.
For both many developers/companies have introduced frameworks & libraries to make life for webdevelopers easier. Think of React.js (JS), Vue.js (JS), Bulma (CSS), Tailwind(CSS).
But the fact remains that many developers still prefer one over the other.