They don't know how to use Lucas Black
He was basically a different character here than in Tokyo Drift. In TD he was a folksy, cool street racer with serious driving skills. Here he gets a few scenes where he's more or less treated as a buffoon and comic relief.
Also, I have to ask: Is Lucas Black okay? He's very thin now, looking almost sickly. He didn't look like that in his younger years. Someone up the man's caloric intake and get him a good trainer!