I understand this, even though the constant breaking of GTK apps after each update annoys me to no end.
But you might want to discuss updating https://www.gtk.org/ and other sites for that matter. Quoting the first lines of the home page: "GTK+, or the GIMP Toolkit, is a multi-platform toolkit for creating graphical user interfaces".
And then you go to the Features page, with a box on the right clearly listing "GNU/Linux and Unix / Windows / Mac OS X" as supported plartforms :) With "Native look and feel" in the box just below.
I disagree with the current GTK direction, but it's not my project and I accept that. If the focus of the project has changed, update the website(s) and documentation.
Benjamin Otte recently added uxtheme.dll support to the CSS engine and I've already seen a few screenshots of the win32 theme using it to okay effect. I wrote a patch to add OS X cursor support to GDK last year and it was taken, not to mention work by Christian Hergert and others to improve the relatively new GDK/Quartz backend. So I'm pretty sure Windows and OS X are supported platforms :)
But you might want to discuss updating https://www.gtk.org/ and other sites for that matter. Quoting the first lines of the home page: "GTK+, or the GIMP Toolkit, is a multi-platform toolkit for creating graphical user interfaces".