I meant "economic systems that work to keep everyone identically wealthy".
Even if there is no cheating, no corruption, no flawed human behavior I would argue that the above goal is beyond stupid.
I work hard, someone else sits around making hippie songs nobody gives a shit about. We both should be compensated equally. Well if that is the case, fuck the 50 hour work week, fuck the continual skill development on my part, fuck the stress of managing an enterprise database. I will write hippie songs nobody gives a shit about (and likely do a worse job than the guy in the comparison).
Multiply that by billions and global GDP declines on a massive scale.
People shouldn't be compensated equally because talents, skills, productive capacity vary. Capitalism is horribly flawed but it is the best system to match the needs of the population with the talents/assets/capital of the population.
It works because it doesn't require you to look out for the common good, nor does it expect you to. Companies engage in brutal "combat" and to emerge victorious requires a better product, or better marketing (which is another product), or better prices (= production efficiency). The entire system is made stronger because talents, resources, and capital flow to where they have the most benefit.
Sure division of that "pie" is uneven but Capitalism makes the pie bigger. The "poor" today have a far better quality of life than say as a poor serf in the Middle Ages. Their slice of the pie is smaller than say Donald Trump but the pie is magnitudes larger.
TL/DR version:
You build a system (even perfect) where the "slices" are even and you have broken the linking of work/assets/capital and reward. There is no reason to be better because even if you are your slice isn't going to get any bigger.