It's really too bad that XML+XSLT didn't take off as the "replacement" for HTML. Before you recoil in horror hear me out... Web pages are a giant mess of content and presentation, and CSS doesn't really help much. XML is at least a way of describing data in a meaningful way. , , , etc. XSLT provided a way of formatting XML in the browser . Sure the internet would still be full of inconsistent content structures, but…
Actually, that was XSL:FO.
XSLT is transformation, not formatting; of course you could translate to (X)HTML with embedded styles, or XSL:FO or something else that includes formatting, but XSLT doesn't do formatting itself.