I don't have to context-switch and open a different file to be able to reason about the styling on an element

Unless you're coding on a VT100 terminal, you just put the HTML in one window and the CSS in another. Subdivide as necessary, or as your monitor space allows.

Heck, we were doing that back in 1989 on IBM PCs with MDA displays.

If your CSS is so out of control that you can't wrap your brain around it, it's time to refactor or split into individual CSS component files.

Maybe even split it into a set of small reusable coherent utility classes