Notice that the Slack app has a similar layout on both mobile and desktop, with a list of teams on the left, followed by channels, followed by the channel content. There are no device UI framework specific elements anywhere, it doesn't use iOS or Android style buttons nor is it designed with Fluent Design on Windows or HIG on macOS.

Agreed that this is a good example where designing for everyone ends up with a worse product for everyone. Same thing goes for Teams, GitHub Desktop, and Postman.

It's horrible having to constantly context switch _within the operating system I am using right now within this very moment_. Context switching when switching devices is not a problem at all.

I wouldn't say worse, I appreciate not having to context switch between different devices.