My best argument against living in simulation is similar to the argument against the intlelligent design or solipsism - if you could simulate anytning, why would you simulate this?
So many things in universe make sense if they have happened by accident, but make no sense to include in an intentionally created simulation.
If I would have the power and intelligence to create/simulate a universe, there's no way in hell I would make the world to work like this.
Have you saw those YouTube videos about genetic algorithms teaching a thing to walk of fly? You may think: this thing do not suffer or feel any pain in repeating millions of times the same moviments just to fall on the floor less and less, no problem at all.
Advance a thousand years in the future and someone may happily simulate the world where you live among trillions of another things trying to evolve.
Simulating a universe like your own except simpler would let you spot-test solutions to problems, and study analogous of issues in your universe to greater depth.
We do economic simulations all the time, with weak-minded agents.
An argument from personal incredulity is still a logical fallacy. It's easy to see why this line of reasoning doesn't make sense.
If we're living in a simulation the thing most likely to running the simulation is ourselves, in the future.
It's easy to see why that would be valuable, e.g. this could be a simulation to see what happens if a war broke out in 1914, and all the downstream effects on that happening.
I think simulations will be used to help people live more productive / happy lives in the future. Imagine having many "lives" worth of experience, perhaps from many different periods throughout history, and you're still only 16 years old.
Not just the "matrix" flavor where the goal is to learn specific skills. I'm talking about being born, growing old, and dying in a simulation many times in a matter of hours? / days? / weeks? and being able to recall those experiences / decisions and their rewards and/or consequences once you're back to living your "real" life.
So many things in universe make sense if they have happened by accident, but make no sense to include in an intentionally created simulation.
If I would have the power and intelligence to create/simulate a universe, there's no way in hell I would make the world to work like this.