For me, CSS has been a Solved Problem™ for 5 years now.

If a website is small then I write plain HTML/CSS/JS in the old school way and all of these abstractions/systems are YAGNI.

If a website is large enough for these abstractions to matter then I'm using React with inline CSS. I get reusability and composition without a noticeable performance tradeoff. You can still build your components to decouple style from content where needed. Up to you.

Years later, no issues.