First, there is no guarantee that a backend and frontend developer together perform better than 1 full stack developer. It really depends on who's doing the job. I'm a full stack JS developer, and yes I can do pretty awesome CSS if needed, or is that considered to be impossible?

Btw, how would the author go about building a nodejs SSR React application? 1 backend, 1 frontend and 1 HTML/CSS guru? I've actually never seen that, even in large companies.

I see there is some frustration about CSS in JS while writing in object notation is not any more difficult than CSS or SCSS, my 12 year old daughter would learn that in a snap. I can imagine it is frustrating for people that are good in HTML and CSS that there is not much work if you cannot actually code, but that doesn't mean there is a problem with full stack.