Right, I misunderstood you and I agree with that. I suspect CSS might always have some cliquey tools like this because although it's fundamentally not too complicated, it doesn't suit all people's ways of solving problems (visually or otherwise) - they'll always reach for something that helps them abstract it some other way or patch holes in their understanding of the language.
I meant "fad" in the sense that it's really popular right now, but it'll die down later on back to the few that it really clicks with.
I doubt it'll be the standard across the styling ecosystem, it'll be like Svelte, or at best like Vue, is to React.