I don't think thats the point, the point was no matter how young and no matter if it was through election or some monarchy. The point is that there were still young rulers in our own history, so it doesn't seem that big a deal in Star Wars.
first off there is a huge difference between electing a leader and having one forced on you.
Second if you actually look at what young rulers have done it's not very much. They are more of a figure head until they come of age. They are groomed if you would and they have strong advisers who instruct them how to rule until they are usally in their 20s. Then they are given more power.
Perfect example is Cleopatra and her little brother Ptolemy XIV of Egypt. Cleopatra actually ruled while her brother Ptolemy was just a figure head although he did have the power to send many of his servents to their death and he did so, he had no actual say in the running of the country or it's people.
Even Alexander the Great wasn't proclaimed King until he was 20 and even then he didn't have full power his mother did a lot of the decision making.