Not long from now all creative and productive work will be done by machines.
Humans will be consumers. Why learn a skill when it can all be automated?
This will eliminate what little meaning remains in our modern lives.
Then what? I don't know, who cares?
Growing tomatoes is less efficient than buying them, regardless of your metric. If you just want really cleanly grown tomatoes, you can buy those. If you want cheap tomatoes, you can buy those. If you want big tomatoes, you can buy those.
And yet individual people still grow tomatoes. Zillions of them. Why? Because we are inherently over-evolved apes who like sweet juicy fruits. The key to being a successful human in the post-scarcity AI overlord age is to embrace your inner ape and just do what makes you happy, no matter how simple it is.
The real insight out of all this is that the above advice is also valid even if there are no AI overlords.
The philosophical problem that I see with the "AI overlord age" (although not directly related to AI) is that we'll then have the technology to change the inherent human desires you speak of, and at that point growing tomatoes just seems like a very inefficient way of satisfying a reward function that we can change to something simpler.
Maybe we wouldn't do it precisely because it'd dissolve the very notion of purpose? But it does feel to me like destroying (beating?) the game we're playing when there is no other game out there.
(Anyway, this is obviously a much better problem to face than weaponized use of a superintelligence!)
In a post-scarcity world we get access to all the cheat codes. I suspect there will be many people who use them and as a result run into the inevitable ennui that comes with basing your sense of purpose on competing for finite resources in a world where those resources are basically free.
There will also be many people who choose to set their own constraints to provide some 'impedance' in their personal circuit. I suspect there will also be many people who will simply be happy trying to earn the only resource that cannot ever be infinite: social capital. We'll see a world where influencers are god-kings and your social credit score is basically the only thing that matters, because everything else is freely available.