Responding out of order...
> unless all you do is live in a web browser all day it's pretty useless.
I think it's aimed at people who live in a terminal window all day, and occasionally switch to a browser, both full-screen.
> I genuinely don't get why people like it
I am working on a story analysing this. My supposition is this:
* I keep seeing people talking about the great efficiency of keyboard-oriented text editors such as Emacs and Vim.
* I have, in the past, had people marvel at how quickly I navigate Windows, because I make extensive use of keyboard shortcuts. (When I learned Windows, on v2.01, my company didn't own a PC mouse; mice were for Mac users. I had no choice.)
* To use Vim or Emacs effectively, you _must_ learn and use the keyboard shortcuts. So many hardcore Linux users do.
* With Windows, Windows-like desktops on Linux, and other mouse-oriented UIs, you don't have to. You _can_, they are there, but you can click or tap your way around.
* So people _do not know_ that there is a whole rich keyboard UI for Windows and compliant Windows-like UIs such as Xfce.
Combine this with the fact that GNOME 3 -- and Unity -- were _specifically designed_ to be un-Windows like, as I wrote a decade back:
The result: GNOME 3+ ignores most of the Windows keyboard UI but it has its own, new one. There is little to customise or tweak, and little window management therefore little UI for it, but keyboard warriors can learn the few commands it has and navigate it with considerable speed.
They believe, like Emacs and Vim folks, that this means it's more efficient. It isn't, not really, but they don't know how to work existing UIs with the keyboard because they never had to.
GNOME irritates me because all the keyboard UI I've been using since the '80s has gone or is broken. (So, incidentally, it is KDE.)