Imagine you take a million humans and you give them a million absolutely identical plots of lands. And each plot of land is, with work, capable of fully sustaining its owner. And you also gave each and every one of them all of the initial tools, training, and resources they'd need to achieve this. And we're also going to assume that these individuals will never experience any health issues or random catastrophes such as weather events, to minimize randomness in our little real life simulation.
And now we set these people free to live as they will. How long will the complete equality last? It'd more likely be a matter of months than years. Some would work harder and produce more enabling them to grow in resources which could then be traded for other things - giving them more than others. Others would go in the opposite direction and behave irresponsibly, such as by indulgence in drink or drug, and find themselves falling further behind. Others would make decisions such as having more children than they could afford to provide for and find themselves in severe issues. Others would simply make better or more astute decisions in general leading them to pull ahead.
It wouldn't take long before our entirely equal society was riddled with inequity. The point of this is that it's impossible for humans to be equal unless somebody enforces that equality. And this brings up two issues. The first is that the enforcer of equality is generally a group or organization that is going to be inherently unequal. Even a completely social system would require 'enforcers' of some sort lest the over achievers dare keep the fruits of their labor for themselves. The second is that you end up with radically warped reward scenarios. If you do better than average, you get stuff taken from you. If you do worse than average, you get stuff given to you. Failure is rewarded, success is punished.
These distorted systems of motivation and the inherent control required to maintain equality are the very fundamental reason that the numerous systems of equality we've tried have all invariably ended up the same. Human society only functions by people spending a pretty good deal of their time doing x when they'd rather be doing y. It's not hard to see what happens when you remove any motivation whatsoever to actually do x. It even explains the ever recurring trend towards authoritarianism and cruel behavior - it's simply an effort to try to force people to do x after you remove all their motivation to do so, and it just doesn't work.