> However I think you have perhaps not internalized yet how CSS variables and scoping rules work have created a situation that allows for often elegantly solving problems that one might wish one had a more powerful query language to handle.

As you already said, this approach would work fine if you had no external payloads that inject their own HTML and CSS on the page, either at runtime or by being loaded by other modules in a CMS.

It also breaks when your :root selector is being polluted by overly generic variables by your platform, like in the most recent versions of Wordpress.