Animal Farm is depressing, really. Big revolt, lots of fun, and then it all goes right back to being the way it was in the beginning. It isn't happy. It isn't hopeful. It's sad. Does any character ever suggest this? Maybe that this has happened before?
Look at some of the characters. Snowball, Squealer, and Napoleon are the pigs. Pigs rule. Pigs are happy. Not sad. They lie and cheat. They aren't good. But they don't see anything wrong with their actions. They think they are great. Orwell's contempt does not fit with their joy. Except maybe Snowball. Snowball, however, is still a pig. Still a power-hungry pig. And he's banished. No author can be in the story partway through. They have to be there all the way through. Boxer? He's another sad case, but he also is removed early. Plus, he was a simple worker. Common laborer. Tried thinking, but fell short. Not an Orwell guy. Chickens? Geese? Assorted other animals? Look who lived through the whole thing, as they would be the ones to consider: Clover. Benjamin. Moses. Pigs. Clover continued working tirelessly. The horses were laborers, unintelligent and unthinking. So that leaves Benjamin and Moses. Moses is in with the humans. He helps the humans. A bleak job, but one Orwell would not approve of. The humans (and later the pigs) use the animals and abuse their labors. Helping them is not good in any way. But that stubborn mule.