It depends a lot on the context if that context is React. CSS in JS in retrospect looks like a shim for react developers who couldnt rewrite their code to single-file components like in Vue and later Svelte. You dont have to be a genius to know how to name and structure dom elements, though being good at it lets you reuse css and reduce overall app size better than any bundler ever will - but its just easier to install Tailwind.