Lean on the primitives we already have, enable flexibility, and if someone wants to make a SaSS wrapper or CSS function to do it, enable that vs. more random places for browsers to diverge on "standards".
It plays out like this:
"Oh, I wanna change the UI element style, thats a new feature! Accent-color! Nice. Oh wait, browsers are doing different things. Dang. Am I okay with that? vs. "I wanna change a UI element style, Oh, browsers now support classic CSS styling attributes on these elements! Nice! Designers sets colors, all browsers just read the designer's palette.