That is an absolutely fallacious argument, since those compatibility issues have ONLY begun with iOS 7 itself, not to mention the fact that at least 50% of all iOS users are still on iOS 6 or earlier, without ANY fragmentation reported until now software-wise.
i think this is the main point, Apple tries to drive home their anti-fragmentation system, and buildup their adoption rates. they want to appeal to developpers and allowing anyone at anytime to go back looses them a competitive edge. at the end of the day youll get used to it and move on.
also, anyone remember when facebook introduced the home page? i remember the petition going around and all the anti-zuckerberg stuff, pretty sure no one remembers what going on facebook was like before the newsfeed