I use XQuery to transform XML data. Whatever can be done with XSLT can also be done in XQuery. It is a functional language and, unlike XSLT, it is supported by more tools for newer versions (XSLT > 1.0 is only supported by Saxon, as far as I know). Overall, it feels much more modern and ergonomic for querying and transforming XML. Best of all: XQuery 3.1 supports JSON natively — I have also adopted it for JSON in some ETL pipelines.

Check Wikipedia for more information: https://en.wikipedia.org/wiki/XQuery