It cannot be simulated because many aspects of military capability are a secret by design and as a matter of functional necessity. The available information is

It cannot be simulated because many aspects of military capability are a secret by design and as a matter of functional necessity. The available information is supposed to be inaccurate. Uncertainty around capability and causality is a fundamental part of the deterrent and battlefield shaping effects during conflict. How do you prove the fidelity of the simulation with respect to actual military capabilities? How do you prevent a party from claiming capability in the simulation that they do not actually possess? Countries like Russia constantly churn out supposed super-weapons that are routinely found out in real combat. If war became all about simulation engineering rather than actual capability, a country is going to recognize the arbitrage opportunity and take advantage of it in the physical world. It is a bit like conflating e-sports with the real thing. One is not a substitute for the other because the constraints and incentives are fundamentally different, optimizing for very different things in execution.