> using features that don't exist in an older version

Except they broke the old way for existing features, required you to use the new way and in most cases you could manually write code so it would still work with both. Meanwhile the only tooling provided by the python 3 crowd screwed over anyone with an existing customer base stuck on python 2, which at least early on should have been a foreseeable problem. Not to forget that anyone stuck on python 2 was literally Satan and projects where outright "shamed" to drop python 2 support.