Earlier quoted context omitted.
The py2 to py3 transition seems to have gone very poorly, although most of the pain from that is behind us now.
Honestly I blame the community. The transition was slow (Python 2 was supported in parallel to 3 for a long period of time so there was more than enough time to migrate), relatively easy to do, and brought huge benefits to the ecosystem. It could have been done and forgotten in 2 years if some community members had not been dicks about it.
JS devs have been transpiling for years now and it works.
Python should have released a conversion tool that could automatically convert most stuff and identify the stuff it couldn't convert. This kind of directed upgrade would have made the process much easier for developers to actually accomplish.