What would they change? These are the best of the best. They have the best and most intense training available, they all have years and years of experience. The game is very very fast and they are expected to make a call in a split second.
I didn't realize how hard it is to referee a game until I did. I'm doing high school ball when home, even that is really fast. It's easy to see from the stands or on tv but when you're at their level, on the field, it's quite difficult. You have things to key on, on every play. Sometimes you think you see something so you hesitate your key progression for an instance to verify what you think you saw and miss something that just happened right in front of.
It won't change, it's part of the game. They could do a replay on every down, you wouldn't like that. They will then catch everything and the game will suffer.