I already hated Office's Save and Open dialog boxes for a number of reasons. 1) They are not OS standard and thus not the same across all apps (also working on Mac where all open/save dialogs ARE the same) 2) they are not consistent in UI (too long a rant to insert here but I am open to speak to a MS UI expert to explain live over Teamviewer for example) 3) the open the virtual door to other apps inventing their own open/save dialog (like Adobe Acrobat is doing .. argggg)
Now Office has an even newer dialog box for first time save. I HAAAAATE IT.
If you're used to using the Save As dialog box from earlier versions of Office, you can go back to using that. Click File > Options > Save, and then check the Don’t show the Backstage when opening or saving files box. The setting applies to all your Office programs. If you want to use the Save As dialog box without making a setting across Office programs, just press F12 instead of Ctrl+S when you save a file.
Yes you can disable both Backstage and the new save dialog, but what if your only beef is Microsoft shifting the default storage location to OneDrive?
"Well the user can change the default..." - Screw that! Most of the time users don't know what they are doing when something unexpected happens. Organizations need the ability to control this stuff - from day 0, not in the next deployment cycle, or after they get X number of complaints.
Ideally Organizations should have the option to freeze the behavior of the software and "Allow" new functionality after it has been risk-assesed and all users retrained.