Comments of chapter undefined of Crows x Souls

Why can't he control flames and launch concentrated flame attacks like he did with his Sharinghan? That way the ways that others have to stop them would be almost null, or are you deliberately nerfing it? I don't understand why the authors give powers that sound magnificent but they immediately put buts everywhere. At least we should be told what will be the way to eliminate its disadvantages in order to take it into account and not be left blind and deflated after the dramatic presentation of a power. That way the author doesn't conveniently change the impact of a character's power in a fight.