This is about Banks's The Culture series, but doesn't really contain spoilers.
Within The Culture it is established that biological humans are nigh-immortal, but that nearly all humans eventually choose suicide after several centuries of life. When I first heard this I thought it was just typical Deathist BS. The same "Ho ho, living forever is terrible, no one would want to do it unless they're an evil villain" crap we usually get. I failed in properly giving Banks the benefit of the doubt. (In my defense, I didn't know anything about him yet, knowing only how immortality is portrayed by mainstream media).
Upon reading The Player of Games, I understood why humans in that society choose death. The Culture is explicitly post-human. Anything of actual importance that needs to be done on a galactic scale is done by the Minds. For humans to feel important, their only option is to be important to each other. Unfortunately, that's also not really an option, because no one needs anything.
At first, this seems like a blessing. That's the whole point of getting post-scarcity. To truly need something is to be in peril. If you need something and can't make/grow it yourself, you're at the mercy of someone who can. Your best option is to find something they want or need and trade it to them for what you need. But ideally, you want to need as few things as possible.
In The Culture, no one needs anything. Everyone is given all the food, health, entertainment, and resources they could possibly want. No one relies on anyone else for anything. No one requires someone else to get any need or want met. And while it's nice to finally have the safety and security to know that "no matter what happens, I'll be fine," it also means that no person is needed by any other. I don't want to need anyone. But for me to not be needed by anyone feels... empty.
The Player of Games does a great job of portraying that lack of connection to any other humans. All the relationships that the protagonist has are superficial, trivial things. There are no stakes to anything he does in his life, aside from the one mission he is sent on that we read about. Everything before that was killing time. Everything after that was trivial as well. Nothing really matters, it's all just games he plays. When no one needs you and there are no stakes, you're just killing time. Eventually you realize you aren't killing time for any purpose. Maybe just skip to the end already.
Which makes me feel really weird, because deprivation and insecurity SUCK. We're trying to build this glorious post-human future because we're tired of the suckiness of life, and we want to fix it. I am now somewhat worried about creating a future were no one is needed for anything anymore, though. Not enough to stop striving for it. But... going full The Culture seems like another Failed Utopia.