Agree that structure-specific CSS is unwieldy. However, it's robustness is still a worthy benefit. If you use a white-space sensitive CSS preprocessor, it is not unwieldy, and actually quite maintainable and elegant, since it's structure reflects nicely-formatted HTML. E.g.

  main
    > section
      > main
        text-decoration blink

Thus, things that are easy to change in HTML structure (cutting, pasting, and changing indentation) are similarly easy to change in CSS.