Any claims that Python has a huge backwards compat mission go right out the window when you consider Python 3. 3 was a perfect chance to fix all of the major problems with Python, problems other languages have solved so there isn't even a need to invent things from scratch. They didn't and that's why the community is still split on adoption.
I have no idea what you're talking about. 3.x objectively did fix the major problems and was not particularly inventive in its approach. The fact that they didn't fix more things all at once — and the fact that they still received massive complaints about supposedly fixing too much — is the origin of that backwards compatibility mission. Actually talking to the devs for any significant length of time makes it clear how much lasting trauma was caused by the change, and how much that cemented pro-backwards-compatibility views. And the community has not been remotely "split on adoption" for years; hardly anyone publishes packages advertised as 2.x compatible any more (e.g. urllib3 gave up almost two years ago). But to the extent that there have been any holdouts at all, it's been people who want ancient systems to work, not people who think that not enough changed to merit upgrading.
