I’m not really a believer of the whole simulated universe theory, but I find your arguments against it weak.

You’re basing what is and isn’t easily calculatable off of our experiences. Same with “complexities of the universes”. However, if our world is indeed simulated, there’s no telling what the host universe is like. It might have crazy different math and be far far more complex than ours. Us trying to understand it would essentially be an excercise in futility.