Isn't it possible that our universe is really just an approximation meant to look as detailed as possible? You don't need a universe of processing power to simulate a universe. You just need to make it look believable enough that it fools whoever is in your simulation.
I agree with you, and even if it's not an approximation, it doesn't matter; we can't make assumptions about the size of a parent reality (and its limits on processing power) relative to our own.
