[Crysstalis]

>but Gtk development for any previous major version eventually stops all development.

Then your actual criticism is that those previous versions have stopped development, not that backwards compatibility was broken. The whole thing about "backwards compatibility" is a distraction. And again, it is not a waste of time keeping up if they actually want the new features. If they do not want them then they are free to spend their time maintaining the old versions.

[badsectoracula]

No, my actual criticism is that backwards compatibility was broken, not that previous versions stopped development - such a concern about stopping development only exists because the newer versions were not backwards compatible.

[Crysstalis]

That does not follow. WPF is also not backwards compatible and you have no issue with that, because Win32 is still being maintained so that makes you feel you can ignore WPF. Am I wrong here?