[dangus]

.NET is used all over the place in Microsoft, including many Microsoft Teams services being migrated to .NET. Teams is listed on Microsoft’s .NET customers page.

https://dotnet.microsoft.com/en-us/platform/customers

Teams was originally written before this particular release existed.

[bmitc]

The commenter was referring to Microsoft's GUI frameworks on offer in .NET and not .NET in general. Of course .NET is used everywhere at Microsoft. C# is one of the most popular languages in the world.

They were talking about Microsoft constantly re-inventing GUI frameworks and then abandoning them. For example, you bring up Teams, but Teams is actually an Electron app, which gets to the point of the commenter.