We can't even simulate the dynamics of a simple atomic system in an exact way, without making assumptions. The universe is that but with many many more atoms and complicated couplings. The universe is much more powerful of a simulation than any computer can ever be. Even if you used a quantum computer you'd need as many qubits as that original primordial soup.

Our computers are not more powerful than the "computer of the Universe", they are much _much_ less powerful.