@whitequark I have written xslt and I really liked it.
I even based the entire template engine of my largest personal project ever (web boards software) on xslt.
What I especially liked about it (that was 2010 though) was that it was all about _transforming_ data, and not just a general purpose language with general purpose constructions; so it kinda forces the developer into a different mindset where one has to think about how input maps on the output rather than (which is the case with other template engines) how to write a general purpose program producing the output, or how to put the data in the placeholders.