> You claim to abstract from cave people. How is that the best we can do?

Because that is, in a very fundamental and immutable way, who we are.

I'm saying that we live in an ecosystem, and that creates emergent properties and behaviours. Resource hoarding and interference competition are among those. No amount of consciousness, rational thought, or foresight, can change that.

As long as (e.g.) hoarding resources today makes it more likely for your offspring to succeed tomorrow, the traits that influence people to hoard resources will continue to perpetuate. It's also why, for example, we have the dark tetrad - it works:

Too high of trust creates opportunities for liars. Too many liars lowers trust to the point that it's not profitable to lie. There exists between these two points a stable equilibrium between zero liars and everyone lying all the time, and it's at neither extreme. The same is true for all other behaviours you moralize.

I'm not justifying anything, I'm simply observing the constraints of the system we live in, and inferring that any mode of social organization that ignores or opposes these constraints is doomed.