XML is used a lot in standards and publishing industries -- JATS, EPUB, ODF, DOCX/XLSX/..., DocBook, etc. are all XML based/use XML.
Without being facetious, isn’t HTML a dialect of XML and very widely used?
Also in finance. XBRL and FIXML although I do not know how widely used the latter is.
Yes, there's a handful of niches. Still 1/1000th the momentum it had, or adoption it was expected to get, and nobody under 40 even considers it for new stuff.