Isn't that obvious, based on society's dysfunction alone?
It's not a moral principle. It's an explanation of where we find ourselves. This doesn't mean we shouldn't keep striving for a just society, but we don't live in a just society.
The question is how ? how can you have a just society that everyone will agree upon ? Unless we are invent some kind of eugenics or brain wash mechanism so that everyone has the same believe, same way of thinking then its impossible.
Or maybe we can develop really advance VR so that make possible for everyone to live in their own ideal socity.
We don't all have to agree on everything all the time. You strive in a direction by moving in that direction, there is no end point, no destination, no way to "complete" the process. There doesn't have to be. Life is messy like that, even when people are generally healthy and happy and kind to each other.
Sure, but all meaning and interpretation of life, all ideas on what is right, and so on, are subjective. There is nothing wrong with that, since it's not like objectivity actually exists on the other side of the scale. When it comes to moral questions, what is "objectively right" simply doesn't apply, and isn't needed.
If everybody simply stuck to treating others how they would want to be treated, we'd live in a much better world already, even if it wasn't "perfect", and even if there were disagreements, and it all still always subject to constant learning and reflection.
Our main problems don't stem from out confusion about what we think is right (and by "we" I mean each of us as the individuals that actually exist, not as a collective abstraction), but from wanting what we think is right for ourselves, while having double standards for others, and rationalizations for those.
It's not my system, it's reality, there is no objective morality, and even where people agree on many things, they don't have the exact same opinions and reasons for having them, and so on. That's at all not contingent on me giving you a satisfying answer on such a tricky question about a site I don't even know.
It's not a moral principle. It's an explanation of where we find ourselves. This doesn't mean we shouldn't keep striving for a just society, but we don't live in a just society.