I agree styles are an afterthought in React. I'm starting to grow fond of Styled Components, but even then I still find doing more advanced CSS operations a bit of a pain. Things like global styles, media-queries, pseudo-selectors and nested selectors sometimes require a pretty good understanding of the library's API and almost always require a trip to the documentation.

I'm really quite pleased Vue sort applied the component approach to styles by slapping them in the component file and then left it at that.