It absolutely matters. If you’re tying development to quality of life, which I agree with, you also have to make the absolute claim that Socialist states can’t develop, which I disagree with. Capitalism is only a few hundred years old anyways, and already is failing, ie disparity is continuing to accelerate to unsustainable levels.
First of all, what is a “Communist state?” There’s no such thing, so if you clarify what you are referring to, that would help.
Secondly, clarify what you mean by “failed,” because either you don’t know much about leftist states or you’re using a different meaning of the word “failed.”
Finally, what do you mean “the idea sounds good on paper?” If it sounds good on paper, ie it works in theory, what about reality is an unknown factor? If humans can’t grasp it (whatever that means), then it doesn’t work in theory!