Searle's Chinese Room argument was about simulating a single person, but I think it actually makes a compelling case that everything in our universe couldn't be simulated. As far as we can tell it's not possible to simulate consciousness through programming.

Even though we don't know how to detect consciousness or what creates it, you can be 100% sure that you're conscious. Which means that at least whatever part of you is creating your consciousness is real and not a simulation. Which isn't to say that the rest of the universe isn't a simulation, but at least one part can't be.

And we can imagine what it would be like if we were all "real" consciousness in a simulation. I'm not sure if that would be better or worse than living in the "real" world, since we have no idea what the real world might be like. It might be terrible, and this simulation is an attempt to make a perfect, or at least better world.

The one big fear if this is a simulation is that someone could decide to turn it off at any moment. But there's a chance that the real universe could tear itself apart at any moment too, so from a scariness perspective, a simulation wouldn't be any worse.