It's possible that our universe is a simulation being run by intelligent beings in a more complex universe.

It's not possible that our universe is a simulation of our universe by our descendents, because you cannot simulate a universe accurately within itself. It would be like saying that you can embed a 100k JPG losslessly within another, existing 100K JPG. You can't do it without discarding a lot of information.

And the information would be missed fairly quickly because chaos theory shows that even perfectly deterministic systems can vary wildly over time based on very very small differences in initial conditions.