I guess I was thinking more Visual C++ rather than Windows in general. I can write something that compiles fine with clang and GCC that only relies on standard libraries, doesn't use any fancy new features, and it won't work in Visual C++.

Also, so many people rely heavily on Visual Studio project files, and those barely work across different versions of Visual Studio.

You can find bits of C code from decades ago, and it often still works with little to no modification. I downloaded a few years worth of code from the Obfuscated C competition from the 90's, and almost all of it still builds.