You bring up some excellent points, that the talent level has gotten better.
However, to say that he's the equivalent of Tommy Rees isn't quite valid. Book has good mobility, poses a real threat to run, and has a significantly stronger arm than Tommy Rees ever had.
The full playbook is open with Book at the helm, whereas at least half of the playbook was unavailable to us in 2011 / 2013, simply because Rees couldn't execute the QB run, and certainly couldn't make the medium range throws. Teams simply had to drop back 8 in a short zone, and our offense would grind to a halt.