I evaluated the characteristics of car crashes; what I discovered was that most of the car crashes were unreal, for example, when I crashed into another car, my car didn't suffer much damage (and everyone knows that modern cars are made from plastic mainly), but that was okay (seriously), what it really annoyed me was when hitting large animals such as deers or cattles my car remained intact.
(Example of an unreal crash)
We all know what happen with our car when we hit big animal (obviously in real life), our car is damaged and, well, we ended up very hurt.
That's exactly what doesn't happen in GTA V.
(maybe if GTA IV had big animals, there would be no mad drivers)
That's why this failure would be one of the biggest in the game, knowing it's a simulator.