I also get GTK2 for free. That's not the problem. I'd happily make my own GTK3 theme if GTK3 weren't so incredibly hostile to theme development. It's literally less reliable than Windows Blinds, which is a frickin' hack on top of a closed OS.
It's not a problem of asshole theme creators, it's a software quality problem, and everyone in the Gnome Project's bubble is dancing around it and pretending it's good for the users.
Often that is acceptable advice, but in this case, their issue that:
> - Doesn't break in the next release.
is something that can't be worked around simply by creating your own theme. That seems to be caused by poor compatibility checking (or reckless disregard, as others are claiming), which could bite you even if you create your own theme.
Obviously, you could extend your suggestion to "fork gtk3", but that's likely a significant undertaking and not reasonable for everyone. I think it is reasonable to expect developers to maintain compatibility between minor version releases, assuming they're using semantic versioning, otherwise it's poor communication on the part of the developers.
Then submits bugs and contribute to fix those bugs, it is the way open source works, if you don't like it, go use something else, nobody is forcing you to use it.
What does being open source have to do with having crap policies?
There are plenty of open source projects that don't have those problems, and it's not like the core team is interested in making theming anything else but a clunky hack so that everyone uses Adwaita...
It's not a problem of asshole theme creators, it's a software quality problem, and everyone in the Gnome Project's bubble is dancing around it and pretending it's good for the users.