By that logic, a deterministic computer program wouldn’t need inputs.
What is being claimed by a deterministic world model is that the output (behavior and internal state change) of a human is a pure function of its current state and inputs. Then we try to give inputs that will lead to desired outputs.
The non-compatibilist view of free will is that it is not a pure function, namely that there is a third independent factor, the “free will”, that influences the behavior (and possibly the internal state). If that is the case, there may never be a way to choose inputs that lead to the desired outputs, because the free will could simply void their effect.