I don't think this especially changes the underlying point: anyone using tools which were based on libxml2 or xerces is basically stuck in 1999. Having to find and install custom extensions adds a regular frictional cost which encourages you to just do more work in a full programming language since you know you'll be able to satisfy any requirement that way.

I saw so many developers sour on XML after hitting the “This would be easy if we used XPath 2 but instead it's hard” wall that I wonder if anyone on the relevant standards committees ever thought about how much libxml2 would make their work relevant.