Windows and Office never adopted .NET for client code in the first place except for the Longhorn period in the mid-00s, which burned them and put them off it. If that didn't stop .NET in the two decades between then and now, I'm not sure why it would today. Actually, Windows is just now starting to adopt C# now that AOT is supported (I think the new native Copilot app is C#).
Many Windows Server admin tools (such as Server Manager or Virtual Machine Connection) and MMC snap-ins (e.g. Event Viewer, Hyper-V Manager) are written in .NET Framework 4. PowerShell is .NET Framework 4. Everyone’s favorite bloated IDE (Visual Studio) is .NET Framework 4 as well.
In the Office land, Excel’s Power Query is .NET Framework 4.
Adopting the modern .NET is probably harder due to its lifecycle.
OMG could you imagine writing MMC snap-ins using some sort of plugin declspec import bs in C++? .Net and reflection with Assembly.Load saves so much time and effort to build modular “ship it now, deliver features later, extend it if we fall behind” apps. Not that those are good things, it just means you can defer until your MS PM gets the budget to fill those backfill positions that have been open for 12 months because the hiring bar is astrophysics
