imho the vaunted readability of custom elements has long been available with haml, with added readability by virtue of the indentation rules replacing closing tags. Not sure why it didn't really gain much traction, maybe the pre-processing is problematic when there's no server-side framework like Rails?

This website violates the rule that all custom elements must have a dash in the tag name.

never knew you could do css selectors on custom elements! does seem like syntactical sugar over classes. I do like the current trend with tailwind: style with markup using smaller components. But maybe there is something here with so many components being just styles...