That's really nice, but to me still sounds like the wrong way to go. Instead of reducing something that is too much, that which is too much should not have been

That's really nice, but to me still sounds like the wrong way to go. Instead of reducing something that is too much, that which is too much should not have been added in the first place. We are doing work here, removing, what we have previously added. I wonder how much ineffective styling still remains after "tree shaking". I guess the fancy tree shaking is out of luck, if we add unnecessary styling to elements, which are indeed used. It seems a really hard problem to solve automatically, to transform CSS in a way, that takes care of redundancies and unnecessary styling, while still maintaining the readability, which well crafted CSS can have.