Have you ever carried an application using Django, or Twisted, or Zope, through this process? It is not easy. Many different libraries with various incompatibilities and versions can lead to real difficulties merely in upgrading for security releases. Additionally, unless one is containerized, one must contend with the underlying platform's issues, as the platform must also switch from Python 2 to Python 3.
I understand your opinion: It is the party line. But it doesn't actually help much when the process as described will take years and people only have months, and this is further worsened by the fact that PSF did not have to deprecate the entire Python 2 ecosystem in order to stop supporting CPython 2.7.