[mafalda]

I would not call "Mountain Lion was the best" just nostalgia. The UI was more concise and polished in general. Consider the Big Sur sidebar, on some Apps it acts a shortcut list, on other as a tab bar and on others its used to host hierarchical views. It not only does not improve the UX in a functionality, it also breaks the reading flow as we need to look in the toolbar (left to right) and then on sidebar (top-bottom) as Apple is pushing developers to use it. It's not to say that skeuomorphic design was perfect too.

Using Mountain Lion in 2021 is going to feel less aesthetic than Big Sur just as using System 8 in 2011 felt. Overall consistency and sizing of Mountain Lion is superior to Big Sur if you consider a keyboard and mouse based OS just as Big Sur is superior if you're used to touch input and modern iOS UI.

[queuebert]

Agree. A desktop OS has different needs than a mobile OS, and Apple is trying to foist iOS onto its desktop users under the guise of progress, but really nothing has fundamentally changed about using a keyboard and mouse to interact with the computer in decades. And that experience is very different, if you are skilled, than using fingers.

Of note, macOS has always been very good at having consistent keyboard shortcuts across apps, something Linux is still trying to learn.