I disagree with the claim that if we do not pursue longtermism, then no simulations of observers like us will be created. For example, I think an Earth-originating unaligned AGI would still have instrumental reasons to run simulations of 21st century Earth. Further, alien civilizations may have interest to learn about other civilizations.
Maybe it is 2100 or some other time in the future, and AI has already become super intelligent and eradicated or enslaved us since we failed to sufficiently adopt the values and thinking of longtermism. They might be running a simulation of us at this critical period of history to see what would have lead to counterfactual histories in which we adopted longtermism and thus protected ourselves from them. They would use these simulations to be better prepared for humans that might be evolving or have evolved in distant parts of the universe that they haven’t accessed yet. Or maybe they still enslave a small or large portion of humanity, and are using the simulations to determine whether it is feasible or worthwhile to let us free again, or even whether it is safe for them to let the remaining human prisoners continue living. In this case, hedonism would be more miserable.
Maybe it is 2100 or some other time in the future, and AI has already become super intelligent and eradicated or enslaved us since we failed to sufficiently adopt the values and thinking of longtermism. They might be running a simulation of us at this critical period of history to see what would have lead to counterfactual histories in which we adopted longtermism and thus protected ourselves from them. They would use these simulations to be better prepared for humans that might be evolving or have evolved in distant parts of the universe that they haven’t accessed yet. Or maybe they still enslave a small or large portion of humanity, and are using the simulations to determine whether it is feasible or worthwhile to let us free again, or even whether it is safe for them to let the remaining human prisoners continue living. In this case, hedonism would be more miserable.