This ecperiment has been happening for decades, its called the Amish.
That said, yeah, you can have your little utopian society as long as everyone consciously agrees to it. But what happens when you have 300 million+ people, some of whom have never even considered the situation?
Also, what happens when someone in this Utopia gets sick and can't pull their weight? Going to ship them back out into the dystopian society? What happens when a bleeding heart from within says we should take care of this person with our resources? Then, you start right back down the slippery slope to where society sits now...