alt Hacker NewsI had done a couple of nontrivial projects with XSLT at the time and the problem with it is its lack of good mnemonics, discoverability from source code, and other ergonomics coupled with the fact that it's only used rarely so you find yourself basically relearning after having not used it for a couple of weeks. Template specifity matching is a particularly bad idea under those circumstances.
XSLT technically would make sense the more you're using large amounts of boilerplate XML literals in your template because it's using XML itself as language syntax. But even though using XML as language meta-syntax, it has lots of microsyntax ie XPath, variables, parameters that you need to cram into XML attributes with the usual quoting restrictions and lack of syntax highlighting. There's really nothing in XSLT that couldn't be implemtented better using a general-purpose language with proper testing and library infrastructure such as Prolog/Datalog (in fact, DSSSL, XSLT's close predecessor for templating full SGML/HTML and not just the XML subset, was based on Scheme) or just, you know, vanilla JavaScript which was introduced for DOM manipulation.
Note maintainance of libxml2/libxslt is currently understaffed [1], and it's a miracle to me XSLT (version v1.0 from 1999) is shipping as a native implementation in browsers still unlike eg. PDF.js.