Clang, however, does strive to maintain compatibility with G++. So you can build a library with clang & use it from g++. It strives, and for the most part achieves, to be a drop-in replacement for GCC, which includes ABI compatibility.
There's the widely used Itanium C++ ABI [0], which contrary to the name is actually the one used on x86-64. Without a standard ABI it wouldn't be possible to dynamically link C++ libraries (which includes the standard library!), especially if they weren't compiled with identical compiler versions.
COM and Windows Runtime (WinRT) provide standardized ABIs across multiple languages. With the WinRT language projections, it's just like writing 'normal' code.
So I gather that, much more than previous COM projections and templating libraries, C++/WinRT is much nicer to work with. And you can target the WinRT ABI with Rust, .NET (C#, F#, etc.), Python, and JS too.
I really didn't like C++/CX from the perspective of the fact that it added weird stuff to the existing syntax of the language, and it had no other compiler onboard other than Microsoft. These two probably killed it more than "office politics".
It is a framework for doing Windows development on Visual Studio, follows the same syntax as C++/CLI, in use since 2003, it doesn't matter if anyone else is on board.
Even today no other compiler can fit into WinUI/UWP workflows no matter what, unless one is willing to do lots of under the hood workarounds.
Office politics driven by people without any consideration for paying customers.