Ubuntu is one the most deployed server distributions of linux, and one of the most battle tested. While this post isn't meant to criticize python 3 (I think the language is perfectly fine as is), it's meant to criticize the ecosystem, where one of the most deployed distributions doesn't work.
Yes, but Debian is also very widely deployed and doesn't ship with a broken Python 3 package. I'm just pointing out that your issue is specifically related to Ubuntu. You'd be better off calling your article: Ubuntu is Not A Suitable Platform for Python 3 Development, or something along those lines.
Actually, this exact issue was also an issue in Debian. The bug reports can be found further down in an answer to the same stackoverflow question. It may now be fixed, I'm not sure.
Perhaps the title should be altered. My main argument is that the ecosystem around python3 is what's holding it back. I think the language itself is perfectly ready, and even most major packages have been ported over.
Check out https://python3wos.appspot.com/ . The majority of major packages have been ported over. Most of the bigger stuff is often run independently and not actually imported by other code (sentry, supervisor, ansible... to name a few).
More modular? I think how modular it is, is one of Django's greatest strengths. Don't like django's templating? You can be up and running with jinja2 in less than 20 lines. Don't like Django's user model? Substitute your own, or if you just need a different auth backend, write your own. Have a desire to use a less common DB? Write a db backend. As far as trashing the ORM for SQLAlchemy, there are a number of django packages that aim to do just that.
There is a small number of ways I could imagine Django being MORE modular.