CRT in a form of msvcrt.dll file had a de-facto presence in Windows since the end of 1990s. Later on, since 2018 or so, CRT availability was formalized in Windows API in form of ucrtbase.dll module.
You can read Mingw64 source to see how many hacks they had to do to make it work.
It's very easy to make a win32 program without the ucrt filesytems APIs so long as you don't mind being platform-specific (or making your own cross-platform wrappers).
Using C++ is another matter.