Sorry, i'm struggling to follow what you're asking here.
Whether you style in stylesheets or by some other means (CSS-in-JS?) is an implementation choice rather than something that affects the fundamental pattern. If your components are truly portable, you're already doing things the way I suggest. If they inherit things like fonts and colors from their parent via the cascade rather than via explicit properties, then you don't have truly portable components - their appearance will change when you move them around.
Do you mean inline in CSS / style tags, avoiding visual HTML classes (in which case we're in agreement - there's one way to edit how something looks, though style tags have other issues) or combining either of those with visual HTML classes like this library uses?
Okay, I think we're in agreement and are just crossing wires a but. The main reason i'm loosely okay with Semantic UI is that I just see it as using HTML fragments as building blocks rather than using JavaScript components. I wouldn't advocate it for anything elaborate, but I think it can work well within a certain problem space.
Whether you style in stylesheets or by some other means (CSS-in-JS?) is an implementation choice rather than something that affects the fundamental pattern. If your components are truly portable, you're already doing things the way I suggest. If they inherit things like fonts and colors from their parent via the cascade rather than via explicit properties, then you don't have truly portable components - their appearance will change when you move them around.