The revelance of Animal Farm in the 21st century is the lesson that it teaches regarding the nature of communism and socialism and how both systems do not work. At the heart of the communist system is power, controlled by a few elite who dominate and control everyone else who is made dependent by the state's control of every aspect of human existence from basic survival, food, job, housing to the lifesaving necessity of medical care.
In a Communist or Socialist environment where there is central control, power, authoritarian power focused on controlling the lives of the individual, squashing individual freedom, making everyone the same in the name of "equality" or "justice." When in fact this brings neither justice or equality.
There is no justice, no equality for members of the communist state only repression and misery, suffering and want. The only equality that is rendered by Communism and Socialism or Fascism is to spread the misery, to everyone equally. Except those who hold the reins of power, the few, the elite, the dictators, the Stalins, the Hitlers, the Castros of the world.
The lesson is to avoid this type of government, it brings poverty, it brings misery, it brings suffering. It does not create a utopia, such an existence cannot be, it never was and never will be. Animal Farm is an example of how Communism and Socialism breed corruption, state sponsored corruption of a nature that is shockingly criminal, yet continues unabated.
While Napoleon and the other pigs, dogs and his new friends the humans, the animals who were part of Napoleon's class enjoyed life, spending money they did not earn, living in luxury. While the working class animals, who broke their backs to produce the good that were sold to make Napoleon rich, starved, worked harder and harder and if they complained, they were systematically eliminated, executed.
Beware of government officials, leaders claiming to be able to provide utopia for all, it doesn't exist, it can't exist.