Spoilers ahead.
Lazy writing. The monsters can kill dozens of people in an instance but conveniently they go super slow with the main characters.
The scene where the main character is about to die then the monster gets killed from behind has been done by every movie ever since the dawn of time.
Scenes where the monsters creep up behind them are over used in this film.
I was underwhelmed. The first movie was good because the writers had the audacity to kill off a child at the beginning (which was a shock for the audience), but this movie offered nothing new.