Why? The analogy works just as well for temperature of water in a boiler, and the thermostat that modifies heating power inversely to the current temperature of the water.
Both are scalars in that example, and the basic problem remains.
You have a point there. But going with your example, the ideal gas law (PV = nRT) still models a system where all inputs are known. While not a perfect model, it's much better for predicting the performance of a thermodynamic system than most economic models are at predicting economic systems.
Both are scalars in that example, and the basic problem remains.