He turned his entire population into experts and specialists to give his nation a good chance of winning the war. Then a group of men, who had sufferred 'shell shock' manifested an ability to travel into fantasy. To figure out how they did this, an expert told him he needed a poet. Poets were a specialty useless to a nation set up entirely for a war so he had none to call upon. I see the value of women as inferior only because it wasn't developed at that time, not because women did not do the same things which males did.
Nothing is valuable unless it is valued for what it is.
Suppose you have a musician. The substance of Plato's blunder is that he failed to tap a resource because prejudice forbade him to see that there was another choice.