For comparison, there's 12KB of text on the page.

There's something about writing 30KB+ of code, plus chunk of CSS-in-JS-syntax, and then using the energy of every single visitor's machines to duplicate the work at a massive scale to generate another chunk of CSS that the browser then has to parse, after executing that JS, which you could've just generated once on the server, that feels fundamentally wrong. IMHO this flagrant disregard for resource consumption is one of the reasons why the "Modern Web(tm)" is as unpleasant as it is.