XML and XSLT are still very much in use, especially in Europe and industries where data schematization & long-term retention are important. I’ve written XSLT ap

XML and XSLT are still very much in use, especially in Europe and industries where data schematization & long-term retention are important. I’ve written XSLT applications for use in banking, healthcare, technical publishing, and compliance markets. For you, I recommend checking out the Docbook transformations and Saxon-JS. The former is a tool for publishing technical documentation to HTML, the latter is an compliant XSLT processor implemented in the browser/NodeJS. XSLT/XQuery/XPath are excellent tools for querying and restructuring tree-structured data. There are a lot of people out there who have very little experience but great big opinions: you should ignore them. Note that these technologies are functional programming languages. It will likely take some effort to wrap your head around it all. Michael Kay’s book is a good start, but unfortunately is not updated for the v3 spec.