The UI of an operating system isn't mere decoration which is what a book cover is. The UI is how you as a user use the functionality of the OS. If that isn't any good it has direct implications on your ability to get work done.

But to be fair, macOS still has a better UI than the competition. But if we Mac users don't complain we will not keep the quality up. I think one of the reasons Mac has such a high quality experience is in part because we Mac users have become a picky bunch who complain when Mac products are not up to our high standards.

I am hoping Apple will pick up on some of the Big Sur criticism and do something about it. I only hope for a better product.