The rulers failed to control the relationship between feudal kings and the central government. Local governors made waves again and again to challenge the central government, and civil wars broke out again and again. Even without foreign invasion, people were still displaced by the war.
The imperial education in the Jin Dynasty was a great failure. There were no good emperors in the Jin Dynasty, and most of them were fatuous people who "why not eat minced meat". The people starved to death without food, and the emperor blamed the people for being stupid. Why don't they eat meat without food?
The rulers were very incompetent in foreign aggression. Nomads invaded the land of the Jin Dynasty, just like traveling. They eat, play, kill and rob, and then leave happily. There were almost no successful defensive counterattacks in the Jin Dynasty, and the people were like lambs to be slaughtered.
Almost all the ruling resources of the Jin Dynasty were in the hands of aristocratic families. As the saying goes, "there is no poverty at the top and no potential at the bottom." Born in a big family, not inferior, born in poverty, can only run errands, can not be reused. This is the concrete embodiment of the Zheng Zhi system in the Jin Dynasty. This system cut off the progress of ordinary people, led to the country being dominated by family mediocrity, objectively weakened the country, and made poor disciples lack a sense of identity with the country. This phenomenon was not solved until the emergence of the imperial examination system in the Sui Wendi period.
To sum up, a dynasty with almost no advantages is rotten from top to bottom. How can you not be scolded?