Depends on how you define “desktop.” Mac OS runs on laptops, and Apple laptops are the world’s best for average users. iOS, Mac OS, and iPad OS are all scaled to meet different form factors while sharing a modern hardware architecture (Apple A and M series SOCs) and cloud infrastructure. Macs with M-series chips can run iPad and iPhone apps.There is nothing Apple can do now on desktop that would suddenly spike desktop popularity back up. And why would they? Most of the market don't want to be confined to a dedicated desk with monitor and keyboard. There are a lot more user friendly interfaces and workflows for everyday Joe. Portable devices is the frontier.
If you count all the devices running in the Apple ecosystem — Mac, iPad and iPhone — Apple is far more important than Microsoft these days.
I suspect “new Windows” is an attempt to milk folks trapped with legacy applications, and that Microsoft knows Windows has no real future. This move will allow them to monetize Windows for as long as possible, and the people who switch to Apple or Google OSes will still be paying Microsoft for cloud services (including Office 365), so MS wins no matter what.
Meanwhile the world can finally move on from X86, the Windows registry, and all the legacy Windows goop that has stood in the way of modern computing.