I do not think functions in CSS are the original sin. Why we don’t have them, was a valid question in the 90ies already.

And you cannot emulate functions by using a preprocessor in all use cases.

But what bothers me is the governance model of CSS, the increasing complexity that leads ultimately to more framework usage, not to thoughtful engineering of accessible front ends.

Very soon CSS will be Turing complete and we can have a JavaScript-free C64 emulator. Yay.

We need basically control structures and full access to user input to achieve that.

And we can only hope the vendors get the sandboxing right this time, otherwise we will get a entire new class of CSS based browser exploits.