“What you can customize: You can personalize your ribbon to arrange tabs and commands in the order you want them, hide or unhide your ribbon, and hide those commands you use less often. Also, you can export or import a customized ribbon.”
Wrap text? Alt H A W
Open settings? Alt T F T
Change to page break view? Alt W I. Go back to normal view with Alt W L
Take the border I currently have on the top edge of a cell and swap it to the bottom? Alt H B M Alt+T Alt+B
Paste values transposing? Alt H V S V E. Want to follow the old accelerator? Alt E S V E also works
Power users don't need to care what the ribbon / menu looks like. They learn hotkeys.
Of course that's discounting the idea that a power user would still want to customize their UI to get less frequently used but still common functions into view and keep them there.
Which is what I, an intermediate user, definitely want: at the time the ribbon happened I was in chemistry research. Excel and Word are important parts of that process! And having them work the way I want was valuable to me. Just not so valuable that I needed to learn a huge number of hotkeys. And yet somehow, the ribbon manages to still be in the way rather then letting me keep a productive, dense UI in view for when I am in those tools - which I'm definitely not in all the time since most of the actual job is being in the lab.
The Formatting/Reviewing split was one of the most irritating possible things as a result of the ribbon: I can't keep the formatting tools in view alongside the Reviewing tools? Like, what?
Pre-Ribbon I could have the menus, file operations, font and paragraph settings, and the reviewing tool bar at the top of my screen. I could have the object and image editing at the bottom.
Post-ribbon the exact same amount of space is does a third as much. Reviewing for some reason is now on a separate tab. The menus are less commonly used functions are non-existent, stuck somewhere under "File" which now takes over the whole screen when I open it.
It is not just "different" it's worse. It removes the basic ability to prioritize my interface to the types of tasks I'm doing, in favor of some vaguely defined every-user who is not actually a real user.