Did feudalism create a stable form of government?

Feudalism was a good form of government, but it could use some work. First, the idea of a social structure is unfair because if you were born a peasant, you would never become a knight or a noble, you would just stay a peasant. Secondly, nobody treated the peasants and serfs nicely. Everyone is a human being, so everyone should be treated the same! Lastly, everyone should have the same amount of work, because the peasants did nothing but  work.