It has nothing to do with needing to modify the games files.
It's the stupid level system that started being integrated in Unity.
Like I can understand not being high enough leveled that if I sneak up on someone they might be able to deflect an attack. But if I shoot someone in the face with an arrow or drop on them from 30 feet up and stab them in the neck, they should die. Plain and simple.
You you enjoy freedom of movement I recommend Unity and Syndicate over Odyssey and Origins. Unity and Syndicate had by far the best freerunning of any AC game.