One can argue that the only thing capable of holding our universe's full state information is by definition the universe itself. No problem with that. Thus, WE can't build that simulator. But the whole shebang falls apart when you actually try to infer that what we know as "the universe" would be the "actual universe" if we were a simulation. The "reasonable" inference is that we always simulated things SMALLER than our universe, thus, if we were a simulation, the "real universe" would be quite big enough to hold "our universe"'s state information with plenty of room to spare. The Earth is quite big from an ant's perspective, but quite small from even our galaxy's perspective. Always a matter of scale.