When I used to use Pages frequently I just memorized all the relevant keyboard shortcuts and turned off the entire toolbar. It’s easy: for each button in the toolbar find the equivalent in the menu, and the shortcut is written on the menu item itself. That’s, however, entirely unacceptable for most users.

The sidebar for formatting they added is strictly worse than the inspector UI in old Pages ’09. The sidebar is constrained not to overlap with content, but the user can choose to overlap the inspector. It’s strictly better flexibility for users. If you are doing a lot of fine adjustments to a single text box, then of course it’s fewer mouse movement if the inspector is located right next to the text box, despite that it has obscured other irrelevant text boxes. I dearly miss Pages ’09.