What you say about mobile and desktop OSes is true, although for productivity people still need a full desktop environment (as the M4 iPad Pro proved once more) and they will still need one for many years to come.
Nobody has come up with a true replacement to the fast keyboard shortcuts/nimble mouse pointer/proper window management paradigm yet. It's just that it doesn't have to be Windows anymore for 8 out of 10 cases I can think of.
Personally, I will be transitioning to macOS when the new M4 MacBook Pro models arrive and, in the meantime, I am experimenting with how much I can get away with by using Linux. I am actually surprised by that, since more than half of my everyday work is done in a browser anyway.
But after 33 years I have finally had enough of Windows and Microsoft. It's time.