It's not that hard unless you had some very advanced code utilizing Python 2 internals that were significantly changed in Python 3. However, conversion takes a lot of time and if something works, why should you be forced to change it?
Nobody's telling you to change your codebase. You're free to carry on using python 2.x. If it already works, it will continue to work in its current environment.
So why are you attempting to tell others in the python ecosystem, be it core maintainers, package authors or OS vendors, support your continued use of python 2 for free?
You want support beyond 2020, pay for it.