YES. And...the @whatwg did include serialization to serve XML. They also prove that entire shifts in approach don't have to be limited to any spec/rec/standards org but independently driven. XML, XForms, XSLT remain in use. Medical documentation for example use XML ontologies.

Yes. And of course we saw CSS Frameworks emerge largely because var() - now CSS has functions. It's been a long-standing issue as it's emerging as hybrid declarative and function. Hmmm. Maybe that's a good thing? I tend toward declarative for markup and style as foundational.