This "key piece of foundational web tech" was released 5 years ago and gained prominence maybe 2-3 years ago. Let's not exaggerate its impact. We were perfectly fine before Tailwind and will be fine after it.
Replaced by what exactly? Also, when was the last time a foundational piece of tech powering of the web got replaced by something entirely different?
Also who has decided that CSS is a "terrible foundational standard"?