Having vague rules and subjective calls is totally by design and it makes the NFL a more dramatic league.
The NFL could probably clean up a lot of the BS with officiating but why would they? It adds to the drama, it adds to the discussion, it adds to the emotional attachment to the games.
Plus they can influence games at will, no one is ever surprised by horrible calls anymore, that’s the most consistent part of the game now.
The NFL knows exactly what they’re doing, don’t forget that.