Comment by arp242

Most of the problems in Python 3 were the string encoding changes. It was very pervasive, fixing things was often not so straight-forward, and writing programs that worked well with Python 2 and 3 was possible but somewhat difficult and error-prone.

The rest of the changes were a bit annoying but mostly boring; some things could have been done better here too, but the string encoding thing was the main issue that caused people to hold on to Python 2 for a long time.

The frozen string literal changes are nothing like it. It's been "good practise" to do this for years, on errors fixing things is trivial, there is a long migration path, and AFAIK there are no plans to remove "frozen_string_literal: false". It's just a change in the default from false to true, not a change in features.

"Learning lessons" doesn't mean "never do anything like this ever again". You're the one who failed to learn from Python 3, by simply saying "language change bad" without deeper understanding of what went wrong with Python 3, and how to do things better. Other languages like Go also make incompatible changes to the language, but do so in a way that learned the lessons from Python 3 (which is why you're not seeing people complain about it).