It’s an interesting idea. I can’t even begin to think about how you would prove it one way or another. I did start to think that computation speed might be a limiting factor, but of course time is only our perception of it: the computer that runs us exists outside of our time.
I have heard it says that some (like Elon Musk, I think) believe that we probably are in a simulation, simply because it seems vanishingly remote that we are in a base universe. I’m not sure I buy that argument.
Does it really make any difference? Obviously knowing would make a difference, but if we never get to find out, do we really care?