But did it ever actually work in practice? As I remember it the XSLT backed websites still needed "absurd amounts of CSS microsyntac". You could not do everything you needed with XSLT so you needed to use both XSLT and CSS. Also coding in XSLT was generally painful, even more so than writing CSS (which I think is another poorly designed language).
It is all well and good to talk about theoretical alternatives that would have been better but we are talking here about a concrete attempt which never worked beyond trivial examples. Why should we keep that alive because of something theoretical which in my opinion never existed?
XSLT is template language. CSS is styling language. They have nothing to do with each other. You have data in some XML-based format. You write template using XSLT to transform that data into HTML. And then you use CSS to make that HTML look pretty. These technologies work very well with each other.
It is all well and good to talk about theoretical alternatives that would have been better but we are talking here about a concrete attempt which never worked beyond trivial examples. Why should we keep that alive because of something theoretical which in my opinion never existed?