What is the smallest hill you would die on?

Using tabs for document management (f.e. Browsers, Text-Editors, ...) was a mistake. It would be way better if every document (website, text-file, image, console, ..) was in its own window, centrally managed by an intelligent window manager of the OS that allows quick and easy search between all documents like with a full-text searchable exposè-like view.

Using tabs for document-management was a bad but necessary workaround because Windows is a horrible window manager (despite its name, ironically).

Tabs work best when there is a fixed amount of them (Like with game settings: Controls, Audio, Video, Gameplay).

I could go on for quite a while on this, but I think this is where I stop.