I think you might have misread Simon in his posts challenging the XML community. He has never that I've seen put down XML's basic usefulness for semi-structured, open data expression. Your characterization as "structured XML data management approaches," however, is another kettle of fish, and not a way of putting it that I think communicates XML's strengths.

Simon's main complaint has been with the culture of rigid schematics, and with the bleed-in of the imperative programmer's mindset into XML (notice that he gives a positive mention of XSLT and XProc, which at least in their initial forms stayed away from imperative style). It seems to me that this article continues his points consistently.