The key points from there, regarding your question specifically: 1) inline styles can't use media queries, while there are tachyon classes for different devices. 2) Ditto for pseudo classes. 3) The browser renders them faster.

But I think your actual question was something more along the lines of "isn't styling individual elements considered bad practice?" That has a bigger answer and is more philosophical. I, too, recoil at it, but I'm open to best practices changing or being considered differently in the context of web applications vs web pages.

For example, react and JSX changed my mind about mixing JS and markup and even styling to some extent.

But you're recommending this? This has advantages over inline styles, but doesn't avoid the main drawback of using them: difficulty to maintain and change.