Would a Play-Doh Society Survive?

Plato's society disregards human error and circumstance, assuming that much of what causes the downfalls man are problems that can be solved by society. The initial flaw in Plato's city is the assignment of work to individuals who's facilities best fit the position given to them. He explains how this, and only this, is the foundation of Justice within the individual. With political and social Justice growing from the roots of the individual Justice that each citizen has, Plato takes a quick assumption that correctly assigning a man to his rightful task is much easier than it actually is. To match a man to his true skill is not easily done. Looking at many of the adults in our life, their success was achieved later in life, if ever. It is only with experience that these people have grown to know their skills and greatest abilities. There are examples of a person knowing the career they will pursue very early in life, but even then one can question the validity of their choice; how can this person know that this work will be best suited for them? They may well accomplish a great deal and be very successful, but who is to say that they would not have succeeded at something else to a far greater extent? With a plethora of possibilities riding on every second of our lives, there cannot be a best path. There can be a true and virtuous one, I do concede, and there is definitely one that is wrong, but there can be no best path. So within the guidelines of Plato's statement that every man should follow the work that is best for him for there to be Justice within him is impossible to achieve with the knowledge that one can always be better at something unknown. We have tried before to make the same designation of labor that Plato's society would  We have given students aptitude tests, which if done correctly, will decode the great mind of a student and project for him his future, but so often the student decides to follow a path completely opposite to the one laid out for him. In Plato's society this would be a problem because they might well get into trouble pursuing something that is not in their nature, but the student has gained new knowledge of himself and his world. The question then becomes, is a man more Just when he has explored the world, learned of new things and witnessed events that have altered his understanding, or is being dutiful to one's society over one's own interests, even if that leads to ignorance and naivety? Look around and witness the millions of people who have pursued the wrong goals and now bring suffering to those around them, they are what Plato's society would never have, but those same people made the decisions they are now suffering from, on their own. If Justice begins with the individual, how can society create the Just civilian?