You may be right about the convenience of having an existing IP with an established aesthetic, but it being set 10,000 years in the past is not a problem for me. Your assumptions are all based on a preconceived notion of forward human development. Leaving aside the fact that this is science fiction, where our “rules” don’t need to apply, societies don’t develop in a linear way. We ascribe positive, progressive, or forward development, as well as the inverse, to cultural norms, behaviors, and materiality in hindsight because of where and when we are when making the observation, but that observation cannot be a retroactive value statement on the course of development at the time.

So the fact that everything looks the same and institutions are more or less unchanged is simply a reflection of the reach of that society’s power structure and cultural influence, and as mentioned by @cowfodder@lemmy.world, the stagnation of the fictional civilization. Each society is different, and it is impossible to predict what any society will look like in the future. It may be unrecognizable or it may appear to be identical.