This sounds like a knee-jerk reaction that results from not having taken the time to make sure that the criticism lines up with the thing being criticised.
> It blows my mind that there's so much devotion to the tool first, problems second
The problem is clearly outlined here: "Manipulating raw ipynb files is difficult and unergonomic."
OP is not fiddling with his or her editor configuration because of any undue focus/deficiency regarding Neovim. The deficiency is in the Jupyter notebooks editors. In other words...
Problem: Jupyter sucks; my thoughts are always slowed down by having to squeeze them through a low-bandwidth link and the ergonomics hurdles that comprise basic text inputs--I want to go fast, but with Jupyter, I can't.
Their solution: This.