That's true but I can still approximate what the system does with a simpler model. For example, I can split states of the system into n distinct groups, and measure transition probabilities between them.

Thermodynamics is a classic example of a phenomenological model like that.

> That's true but I can still approximate what the system does with a simpler model.

For any strategy you might apply to do that, I can craft a program that similates a phenomenon that defies that strategy.