A simulated world created after the singularity is not necessarily a post-singularity world, if singularity never happened in it. You already don’t get to make discoveries that won’t be available in the future, or in other Everett branches, and simulators are even less directly related to what’s going on within the simulation.
You don’t interact with other Everett branches, or the future, so it doesn’t matter in the same way as what happens in the same world. If you exist within a simulation with appropriate laws of nature, you similarly won’t be able to interact with things happening elsewhere, those things within a simulator won’t be relevant for you in the same way as other Everett branches are not relevant to you within physics.
We don’t get to make new scientific discoveries, new inventions, etc. with superhuman agents.
What self-actualisation means for me seems like it would be absent in the post singularity world?
A simulated world created after the singularity is not necessarily a post-singularity world, if singularity never happened in it. You already don’t get to make discoveries that won’t be available in the future, or in other Everett branches, and simulators are even less directly related to what’s going on within the simulation.
You don’t interact with other Everett branches, or the future, so it doesn’t matter in the same way as what happens in the same world. If you exist within a simulation with appropriate laws of nature, you similarly won’t be able to interact with things happening elsewhere, those things within a simulator won’t be relevant for you in the same way as other Everett branches are not relevant to you within physics.