> CSS isn't powerful enough to style HTML however you want without having to add a soup of extra divs and classes that are only there for styling

Totally this. We say we've come a long way from using tables for layout, but for example you still can't use Flexbox without at least some non-semantic .stuff-container and .radio-with-label junk. Decoupled HTML and CSS have failed in the real world, outside of pet projects.