The reason is: "A gentleman uses people like weapons, each taking advantage of his or her own strengths. How can those who ruled in ancient times borrow their talents from another generation?"

The main idea of ??the full text: Taizong ordered De Yi to Recommend talented people, but after a long time, no one was recommended. Taizong reprimanded him. Deyi replied: "It's not that I don't try my best to select talents, it's just that there are no geniuses in the world today!" Taizong said: "A wise man uses talents just like using tools, each using their own strengths. Could it be that those who were able to govern the world in ancient times? Do you have to borrow talents from other eras? Not only do you not worry about your own ignorance, how can you frame everyone in this world?"

The implication is probably not to ridicule you because of your ignorance? Ridiculing others only makes you appear more ignorant.