Why can't long poles enter the city gate?

The original sentence means: I am not a sage, but I have seen a lot of things. Why not use a saw to cut the long pole from the middle and enter the city gate?

The original text comes from my country's first joke collection "Laughing Forest" (written by Handan Chun from the Wei Dynasty during the Three Kingdoms period).

It is also called Long Pole Entering the City

The story tells What's interesting is that once upon a time, there was a man in the state of Lu who entered the city gate with a long pole. At first he held it upright and wanted to enter the city gate, but he couldn't enter the city gate. When he held it sideways, he couldn't enter the city gate either. He really wanted to Nothing can be done. Soon, an older man came here and said: "I am not a sage, but I have experienced a lot of things. Why don't I cut the long pole with a saw and then enter the city gate?" The man from Lu followed the old man's method. The long pole was cut off.

The irony of the story is that the person holding the bamboo pole does not know how to think when doing things, rigidly follows the rules, and does not know how to adapt. In fact, you can hold one end of the bamboo pole in one hand and put the other end of the bamboo pole on the ground to form a slope and enter the city. If the bamboo pole is placed flatly through the door, it will easily blind other people's eyes and harm other people's health.