[PantaloonFlames]

XSD was (is) not so easy to adopt, but I don't agree that it's a monstrosity.

Schema are complicated. XSD is a response to that reality.

The XML ecosystem is messy. But people don't need to adopt everything. Ignore Relax-NG, ignore DTD, use namespaces sparingly, adopt conventions around NOT using attributes. It generally works quite well.

It's a challenge to get comfortable with XSD but once that happens, it's not a monstrosity. Similarly, XSLT. It requires a different way of thinking, and once you get that, you're productive.