As an opensource dev, I'd just ignore that, for my own sanity. I remember I had a complete build system for MSVC/VisualStudio available in the first opensource tool of some reasonable size I released, "mkd64". I really lost any interest maintaining it. One of the reasons is that MS doesn't move at all regarding C. It looks like they consider C "obsolete" and C++ the "successor". And, frankly, this is bullshit.For a long time they even dropped support for the MSVC compiler. Obviously that compiler is fairly underwhelming, unfortunately so many Win32 middleware developers have tied themselves down to it and thus it is generally important to support for GtkWin32.
It's of course all different if you do development in an enterprise context. But for me, releasing my C stuff as opensource, I just say: grab MSYS2 to build it yourself on Windows if you want. And if you don't want, that's not my problem.
So, I kind of understand where the GTK guys come from