Well sure, nature could all be a simulation. In which case, all I'm describing is the rules of the simulation. Either way, science is the study of nature (of the simulation).

Looping back to the original topic, if it's all a simulation and the moon is part of that simulation, then why is it controversial to say that (simulated) humans went to the (simulated) moon? Why is it controversial to accept mainstream physics as accurate?

Assuming human consciousness exists within the simulation, then it doesn't matter because it is our reality. If consciousness exists outside of the simulation, then that's by definition metaphysical.