I have been using Macs daily for a decade. Big Sur is a big reversion in usability. Easily the worst MacOS update I can recall. The UI is a lot clunkier and slower and just harder to make sense of. They will throw it all out in 2-4 years and start over, that's about how long the UI stays stable.
I think the obsession with making everything white, with no clear distinction between window contents and window chrome makes it quite confusing. I'm hoping they revert this. Not everything has to be flat.
Yeah, modern UX designers need to come down out of the clouds and pay attention to how people actually do work. It isn't just Apple either. Mozilla is doing the same thing with Firefox. The entire industry seems to have their heads screwed on backwards. Second to HR they are the people I trust the least.
