Can agree he certainly should have scored more by now with the time given if you judge everyone by equal standard. If the attacking players include only Messi, Griez, Fati, Coutinho, Braithwaite and Dembele then it's certainly between him and Coutinho for finishing on the volume of shots.
Coutinho for instance takes more shots usually from more difficult positions so you could question decisions. While Braithwaite's NPxG90 and distribution of his chances missed definitely suggests he's getting better looks, but ought to have at least 1 or 2 more goals to his name.
Griezmann by comparison had less chances of this quality, no matter the opponent. Team finds Braithwaite for bigger chances. And that's kind of no small feat considering he's just a Boro reject. You could use the goal return and involvement in chance creation to beat him up, but we all know he's far from the real problem. In fact the opposite - he offers team a solution, even if it's just against the Valladolid kind of sides.