I’ve always felt that the universe is the simplest representation of itself. As such, ‘twouldn’t seem to add much to require it be a simulation.
There is much more to know in physics (given that we cannot explain dark matter, dark energy, and the whole quantum multiple state problem....to list a few things popping around the professional mags nowadays.
We appear to be at a similar situation to that at the beginning of the 20th century - when it appeared that only a few i’s had to be dotted and t’s crossed in order to explain life, the universe, and everything. Turns out the answer then was 42, and drat, the darned number was not even prime. Bummer.
That's a very information-theoretic argument and is the key to understanding why the universe is not a simulation. If the universe is the simplest representation of itself then any "simulation" of the universe would, of necessity, be larger than the universe itself. However the term "universe" means "everything", so positing the existence of something larger than everything would clearly be self-contradictory.