Nothing can be left to chance in this world. Every action, every thought, and every existing thing must be controlled at once by omniscient, immutable beings. Not only omniscient and immutable, but also omnipotent (how could these beings maintain perfect control over everything if they didn’t have the power to do so?)
The wills of these beings must also completely aligned - there can’t be any differences between them, otherwise there could be conflict, and conflict could mean suffering. Everyone has to have exactly the same properties of omniscience, immutability, externality, and omnipotence.
Now, by Leibniz’s law of indiscernibility of identicals, we are left with a singular, omnisient, omnipotent, changeless, timeless, all-good being (see where I’m going with this yet?)
A world that is completely good is a place where cause and effect, space, and time lose all meaning. The nature of an all-good world is incomprehensible to us.
This is simply because the only thing that is truly Good is God Himself. It is impossible to be a finite creature and “just be good.” It doesn’t work like that.
The question, “why can’t the world just be good?” is essentially the same question as, “why can’t I just be God?” And you can’t be God.
It’s literally the opposite of what you’re saying, OP. It would be impossible for God to create a perfect creation. The only thing that can, in principle, be perfect is God Himself.