I've thought about this a couple of times, what happens if we truly succeed and we as a species solves all of our major problems? Like energy, food, health (incl stopping aging). Do we even need economic systems then or will the "market" become obsolete too? So lets say we solve ALL of our problems and we somehow manage to briefly unite humanity to want to dominate each other, meaning we all need to become one race, one language, one cultural blob to reduce all friction (best case scenario - won't happen in reality). How long will it take for human nature to get bored and split into groups and start controlling each other? Who decides who gets to make babies? How many babies are optimal? Who is in charge of this kind of society? What if we all get a non-invasive implant that lets us share thoughts & emotions? What does privacy look like in this world?

I think people will briefly chill out and enjoy it, but after a while, we will be back to business meaning we will create systems and hierarchy to control social order, and so the blood sport continues. Then we might realize the our problem was never energy/food/health etc to begin with, it was an addiction to power and the blood sport it invites. And round and round we go.

I also think, the moment AI becomes an actual threat (threat meaning a better/smarter consciousness) - the human brain will immediately try to eliminate it to keep its dominance. If not, we will go the same way as neanderthals.

edit: The movie Jupiter Ascending also has an interesting take what might happen once we solve our problems - then we try harvest Time.