I disagree that it is sad way for Franks to go out. He already has two World Cups, multiple Super Rugby and Championship trophies and has represented his country more than 100 times. He has nothing more to prove, he’s already been there, done that (and got multiple T-shirts).
Of course it's sad that he can't finish on his own terms. It's not a tragedy, no one died, but to be dropped on form rather than retire is sad for such a great player and reasonably unusual.
To play over 100 tests over 10 years is a huge achievement and only the great players