POD is too simplistic for a lot of the tasks people use for HTML. While it makes for a decent, minimalistic documentation system, it's rather lacking as a full layout system.

YAML is mainly for cross-language data exchange which is reasonably readable by humans. I don't think it would work well as a layout system.

In any case, while old-skool HTML sucks, XHTML+CSS+XForms fixes most of my grievances. It'll be nice when we can actually start using all those things in real web pages.