The author is an interesting character of strong, often contrarian, opinion. He's also the guy behind the Calibre e-book software, which was largely written in Python 2 long after that was deprecated. He even wanted to maintain Python 2 himself rather than rewrite Calibre, but he eventually realized that wasn't feasible and ported Calibre to Python 3.

This reads as if he started Calibre when Python 2 was already deprecated..but to be clear, it was started some years before the first release of Python 3, 14 years before the deprecation.

And at the time of the beef, many bigger apps were not ported yet (some even till today). The authors' opinion was more an extremer version of something the whole community felt at the time.

Incredible popular software lore here. Calibre and Kitty are two of my favorite pieces of software in the world.