They changed a ton about the UI in Big Sur, none of it for the better as far as I can tell. They took away even more choice, I can't have a "classic" desktop experience.
My biggest frustration is that they were willing to make such drastic changes to the desktop UI at all. I have to re-learn a ton of keyboard navigation now. And there doesn't seem to be a coherent design to the workflows.
Such a drastic change seems to be an admission that they thought the previous design language was wrong but they seem to have replaced it with... no vision at all?
I am hopeful for the next generation of M1 MacBook Pros and whatever the next MacOS is. Hopefully they get their design philosophy straight and stick with it.