The real question to ask is: what is the difference between a simulated universe and a real one? Heres a hint: If the simulation substrate is unconscious or naturally occurring, is it still a "simulation"? Or just a real universe with extra steps?I think that most people would agree that a universe only counts as "simulated" if it was created by conscious beings intentionally.
In other words, proponents of simulation theories have basically reinvented god. But they've done something even more mind bogglingly self important: by posing God as a sysadmin of a celestial server farm, they have essentially written themselves into the role.
From a certain point of view, this kind of behavior from self proclaimed rationalists is pretty hilarious. It's also deeply human. But ultimately it's also very silly.
In ancient Greece the gods were fickle, horny warlords; in medieval times God was seen as an absolute monarch. And now, he is being posed as an overworked it professional. And that is absolutely fascinating for what it says about our culture and psychology. But it says nothing useful or testable about the universe.