Kallipolis, as described in Plato’s Republic appears to not allow for any societal growth. To understand this we must separate the longevity of The Republic as a whole from the longevity of Plato’s Kallipolis. Though not intended to be an exact blueprint of an ideal city, Kallipolis is used as an example of a just society.
This society seeks to fulfill the individual’s basic needs but does not take into account the individual’s thoughts, desires, or humanly vices. Later, Aristotle would say that to develop character, you need to have certain traits. For example, to be human, there are certain traits, virtues, and vices. Plato leaves no room for uniqueness, where there is a combination of your roles as an authentic individual. In Kallipolis, there isn’t really any room for movement, everyone has a vocation. This is seen in the Myth of Metals, where everyone is divided up into gold, silver and bronze or guardians, warriors and producers.
In this division of Plato reduces us to a single role, and does not accept any potentiality. He argues that a person would do better work if he only practiced one craft (370b5, pg. 48). Arguably, humans do have strengths and weaknesses, but the citizens of the theoretical Kallipolis would not be given the chance to explore these things. The greater good mentality totally loses the individual. Plato’s utilitarian ideals focus too much on the aggregate good.
Because of this, he has not truly come up with an ideal society because it could not withstand the test of time. An ideal society would be dynamic and able to adapt to new technology, scientific discoveries, social movements. It would support both the individual and the community on equal levels.