Yeah, XSLT 1.0 has some really obvious missteps, so much so that to my knowledge basically nobody just implements XSLT 1.0. What they actually support is (most of) XSLT 1.0 plus a handful of EXSLT extensions (which are completely unofficial and not part of any XSLT spec, by the way). In my opinion the EXSLT stuff is the bare minimum needed to make XSLT 1.0 at least a passable language. Meanwhile, the XSLT spec evolved into 2.0 and 3.0, which as far as I'm aware, even to this day, has no complete open-source implementation.