Whatever gave you the idea Microsoft "left" C++ years ago? It has massive code bases in C++ and continues to invest in its compiler teams and actively tracks the C++ standard. It was the first compiler to implement C++20 mostly completely, including modules, which other compilers have yet to catch up to. Like other mature companies, Microsoft realized decades ago that they can be a one-tech-dependent company and hence has code in C++ and .NET, and is now exploring Rust.
Cppwinrt is in maintenance mode[1]. Cppwin32 is abandoned (with windows.h as the official alternative). It is now possible to deploy WinUI 3 apps as single files in C#[2] but not in C++. From experience, the entire C++ side of WinUI 3 documentation is underbaked to the extent that the easiest approach is to read the C# documentation and attempt to guess the cppwinrt equivalent (as docs for cppwinrt are not really... there).
I don’t know if they’ve really abandoned C++ entirely—the compiler team certainly hasn’t, that’s true. But the above doesn’t feel like first-class support.
[1] https://github.com/microsoft/cppwinrt/issues/1289#issuecomme...
[2] https://learn.microsoft.com/en-us/dotnet/core/deploying/sing...
WinUI3 itself feels kind of abandoned. Heck, everything except desktop OS (which changes we neither need nor want) and cloud (where everyone has gone) feels a bit neglected.
C#/dotnet continues nicely, but the team is surprisingly small if you look closely.
Microsoft doesn't commit to UI frameworks in any language. By contrast, DirectX 11 and 12 (and Direct2D) are C++-native and have become core modules within NT. I don't think MS has abandoned C++, but the use case for C++ has shrunk considerably since the 1990s
If you go into Visual C++ developer blog, you will notice it has been all about Unreal support during the last year, and not much else.
Besides the sibling comments, officially Windows is going to go under some rewrites under the Secure Future Initiative, and the MSVC team has been reduced in resources, to the point now they are asking what features of C++23 people want to have.
https://developercommunity.visualstudio.com/t/Implement-C23-...
I suppose usually one would like to have everything from a language standard.
The C++20 winning run seems to have been one of a kind, and whatever made it possible is now gone.
Speaking of gone, Herb Sutter has left Microsoft and most certainly had to do something with whatever is going on MSVC, C# improvements for low level coding, and Rust adoption.