It sounds like the cost was non trivial for them, partially because they weren’t allowed to break things for python2, or even disrupt the efforts of those using it.
The language wasn’t ready for the transition, but it feels like it may have been even harder on them because of the requirements imposed on their project.
Most of what opposition there is comes from people with projects which are some combination of under-staffed, poorly tested, or with a marginal approach to scheduling necessary maintenance work. That is not a great place to expect to find reliable maintenance contributions.
Where you are more likely to find this is from the major Linux vendors: e.g. Red Hat is committed to support it through 2024 and I would expect that they won't be alone in offering paid support for remaining users.
I'm actually (pleasantly) surprised that someone like Google (or a league of someones like Google) who have deep pockets and so much Python 2 that it's cheaper to maintain Python 2 than it is to port to Python 3. Perhaps they (correctly) were concerned about the ecosystem moving on toward Python 3, leaving them behind?
Right, they could have paid a nontrivial cost (asking devs to use b-strings, print_function, etc) but didn't by fiat, choosing instead to pay a greater cost during the migration in addition to the nontrivial cost. My comment expresses skepticism about that decision.
The language wasn’t ready for the transition, but it feels like it may have been even harder on them because of the requirements imposed on their project.