Another big problem is there was no significant incentive to adopt Python 3. That’s why it took so long for large projects to transition. In comparison, during the last decade, C++ went from dodgy C++11 toy projects to all new code being written in modern C++. The modern feature set is that good.
That’s a find-and-replace fix that can be addressed reliably. A relatively smaller problem versus moving off of boost.
The compiler support for C++11 (and especially inconsistencies in Debian packages, compiled flags, etc) was a very painful issue for several years. But auto is that useful ...
Right, moving to std::cout to fmt could be as simple as a find-and-replace fix. That the C++ committee could have inflicted this minimal pain on their users, but chose not to do it, shows some amount of concern for backwards compatibility and old codebases. By comparison, Python 3 changed the entire text model and dropped the mic, and waited for 8 years to start to pick the pieces back up.
I guess I don’t understand your argument that “Python 3 changed the entire text model and dropped the mic.” format strings are optional; the old % operator still works fine. The change to unicode is dramatic, but personally I haven’t run into major problems. I’ve had unit tests break because of it, but that’s why one has unit tests. I’ve also worked on a very large python webapp that underwent painful internationalization, and in that case we ended up using unicode strings everywhere anyways.
