The Microsoft moat is 3 fold;
- Office (Excel and PowerPoint)
- Active Directory
- legacy Win32 apps
It isn’t that Windows has a desktop competitor, it is just that generations of people are being born with the idea that they never need to go to a desktop platform - period - (to get their work done). Use cases of all sorts have migrated from Windows to non-Windows platforms for a variety of reasons.
Purpose-built OS, low power consumption, environmental requirements (operate in cold/warm temperatures - with utilitarian / industrial designs), easy to manage - Windows computers are just disappearing from the world. The alternative is cheaper to maintain, replace, manage. On the flip side - people are doing just wild things on mobile - like video, photo editing (basic stuff, but not insignificant tasks compared to just 5 or 10 years ago).
Food for thought: 2 years ago; there were over 3 billion android devices in use, and only 900 million Windows devices.
Children today don’t grow up with Windows like most of us did. They grow up with Chromebooks. They grow up with Google Apps like Sheets and Docs - which have frictionless, licenseless experiences.
Windows has no competition with Windows, but no one wants to compete with Windows, and Microsoft doesn’t even want to compete with Windows. It could sarcastically be said that no one in technology is trying to solve problems for Windows, or on Windows. The joke with that statement is everyone would be on macOS or a Linux Distro - and working on those platforms to deliver platform agnostic solutions - focusing on HTML5 and mobile native.
The question often becomes; why Windows? Why not just develop a offering that is platform agnostic?
Long-term, this erodes the value of Windows. Certain jobs will have Windows for the foreseeable future, with no alternative. But the use of Windows will still diminish long term.
There are websites that track (by browser user agent) the OS in use across different cities, states and countries. This data is quite fascinating and amusing. You can see trends very easily. Developed countries generally have higher macOS and iOS market share - with a few countries having 40% of desktop users on macOS (when blended with mobile, macOS market share decreases significantly). Frontier economies have massive Android market share, and overwhelming amount of desktop market share to Windows.
These are wild times. Windows is going nowhere, and when people say that; they mean literally. When one of the latest enhancements to the Windows OS is including support to run Android apps; which to me looks like the white flag being waved. In my lifetime, I would have never thought it was possible for Windows to have a native OS clunky emulator for Android apps.