I find myself often wishing conditionals on CSS until I remember that they aren't necessary because things like

    input[type="submit"]{}  

exist (but feel hacky as can be) and that if they did exist I would never, ever want to edit someone else's CSS file. Can you imagine the mess?

It would be nice not to have to look for a style:

1. inline html

2. in the CSS file(s)

3. in JavaScript (or js library)

4. in the source code in the backend

to find that one edit you need to make.

I think that limitation is the most frustrating, that because CSS cannot 'see' beyond its own little home it bleeds out into other documents.

We have variables now <https://drafts.csswg.org/css-variables/> so it's not a mistake that needs a time machine.