LaTeX is something very, very different. It's based around macro expansion and oriented toward print, not programmatic transformation. For example if I want a

LaTeX is something very, very different. It's based around macro expansion and oriented toward print, not programmatic transformation. For example if I want a programmatic table of contents for an XML document it's a simple transformation or DOM extraction exercise. If I then transform to XML-FO that will fill in the numbers. LaTeX does multiple full document renders to obtain auxiliary data for a later render to use. No XML based system does what LaTeX can do for text rendering. It's not impossible they just haven't bothered. What's more impossible is to match the ease of writing text. LaTeX gets in the way much less for most text.