I am an old man and my knee would not have buckled like RG3’s knee on his last play.
RG3 needs to hit the weight room and turn into a rock like Luck. Very large people try to pull Luck down and he simply does not go down and that is because Luck is bigger than RG3.
RG3 will probably lose some speed and shiftiness with the weight gain but it will be worth it in the long run.