Why is CSS such a poor language for layout?

In A Note on Layout Language Richard Mitton gets to the root of why CSS has always felt so clunky as a language for visual layout. It was built to style, its design and its fundamental primitives are suited to that. Layout calls for a different grammar that the cascade is unable to convincingly contort itself into.

How many man hours could have been saved globally if the web had been birthed with a more appropriate layout language based on prepositions rather than the INI style key-value list we got?

— Richard Mitton, A Note on Layout Language