Really?
I believe that moving a 500k loc code base qualified us as semi-heavy. And relying on packages that didn't move qualified us as stuck.
Now - don't get me wrong: i/we liked python2. There was little wrong with the language or sticking with it. But please don't think the cost of migration was a weekend of lost coffees.
Most people I know who complain about the Python 3 transition are not heavy Python programmers.
Migrating to Python 3 was certainly a pain, but not really a major one. The number of developers who fled Python because of this is miniscule. If the Python 3 transition is the poster child of "things going wrong" with backward incompatible changes, I would heartily recommend other languages make those incompatible changes.