I remember reading this book back in high school and thinking it was a critique of communism. This time through, it does not seem critical of communism but rather supportive. What the book does criticize are the leaders of the communist movement. But at the beginning of the story when the animals are closest to living the ideals set originally, their lives are better than previously. This will lead to one of two interpretations: communism is good, but the leaders of the movement screwed it up, or communism is flawed and cannot work because a person in power will eventually abuse that power.
I don't know what Orwell was trying to say but apart from communism I think it is an apt description of the complacency and intellectual laziness of most people.