We can focus effort on maintaining this balance...but doing that requires power to be used. And just like that we are back at step one.
We can communally build up trust to such a high level that everyone can act independently to maintain balance, but this naturally creates a situation where the more trust there is, the bigger the payoff for the one who breaks it. Essentially the prisoners dilemma.
We can just not fight. There is enough room and resources,we can get more of them and build more efficient tech, and we are all more alike than different.
Maybe you argue that we are human and intelligent, so we can override this inconvenience with a system of our own design. My response would be "Sure, put your guns down and burn them, I won't stop you."
Again, it's an unstable equilibrium. Power on the other hand is dramatically more stable.
We don't kill weak links in our population just like mother nature intended and keeps doing left and right everywhere all the time, a good chunk of this forum would not pass those harsh and often random tests yet its/ours added value is non-trivial and surpasses any additional effort by society (at least I like to think that).
'Everything good in this world is kindness'. I have yet to meet a person, situation or story where this would not apply.
(To be clear, not targeting you personally here, but targeting the rhetoric and fallacy)
If everyone else is defecting and you can cooperate with a few people, that's slightly better for you. Hence we have high-trust and low-trust societies, gatekeeping, etc.