Hadn’t heard of XQilla, but looks like it’s limited to XPath 2.

You should try an XPath 3 based implementation. XQuery 3.1 has some nice features not found in XPath 2 implementations e.g. native JSON support, the arrow operator (piping), group by clause in FWLORs. XSLT 3.0 has some nice new stuff too, but I use that less