This is about free software. If a distribution insists on theming your Electron app, it can do so.
Sure. Even if I disagree with the letter, no one has asked for disallowing distros to do anything - it's more of a plea than a demand.
True. It even explicitly says that they don't want to use a technical solution like 781 proposed.
> I would really Electron to add an on-by-default standard interface to override CSS rules for Electron apps
That's a hard problem to solve, since there are many ways of styling Electron - Bootstrap/Bulma/Material Design/custom stuff. So it's hard to just override CSS rules.
On the other hand, it's the kind of problem perfectly suited for Machine Learning - just take the whole screenshot/image of the app and use a stylistic ML to change it - make it Dark Theme/whatever...
I suspect in 10 years OSes will support ML-based automatic themeing/customization of all apps, regardless of what they are written in.
The exact same argument could be made for web apps, but we still have userChrome.css and userContent.css which solves this neatly.
How many are actually using that? I don't know anybody.
https://www.ghacks.net/2019/05/24/firefox-69-userchrome-css-...
(I don't have a horse in the Electron-is-great-or-crap race)