We are talking about software development not user configuration. So “theming” here clearly refers specifically to the applications shipping non-standard UIs.

This also isn’t a trend that Electron started. Software has been shipping with bespoke UIs for nearly as long as UI toolkits have been a thing.

>But Electron said to the entire world "go to town, burn the system Human Interface Guidelines and make a branded nightmare!"

TBH this sounds pretty medieval too.