The perfect OS/Desktop is one you don't even notice, or know is there; it just works. Macos used to be invisible, but then then some ego-driven developer decided to push Apple Glass on to everyone. HEY LOOK HOW COOL I AM!
Although at the rate of LLM improvement, I'm thinking the Next big os, will just be a really good API (gui/sound/graphics...) , you boot to a prompt screen, and then you just tell it what you want to do with the computer and it builds the apps you need from scratch.