Pull down the tiny arrow in the Quick Access Toolbar. If your box beside Touch/Mouse Mode is unchecked, click that. Now Excel will give you the finger. ^_^ It may not help, though, if it's not already there - if you had a touch screen it should have already
been in Touch mode.
I'm not a fan of the wasted ribbon space either. Touch/Mouse could be renamed Worse/Bad.
At least within AutoCAD I can control how big the buttons are on the ribbon and control how they shrink as the window is resized. Office apps just reconfigure the ribbon like maniacs as you shrink your working window. Just give us one interface and leave
it alone.