This is a great question. At first, the revolution started with great promise. Mr. Jones was not a good man; often he was drunk and did not take care of the animals. The narrative makes this point clear:
Mr. Jones went into Willingdon and got so drunk at the Red Lion that he did not come back till midday on Sunday.
So, a revolution sounded great. The rationale was, things can't get worse.
When the animals gained control of the farm, things did seem better. But in small ways the situation began to deteriorate. Here is a little detail that not all was well.
It was noticed that they wagged their tails to him [speaking of Napoleon] in the same way as the other dogs had been used to do to Mr. Jones.
In time the situation became worse. In one of the worst scenes, there is an execution, something that would never have taken place under Mr. Jones. Here is what the text says:
And so the tale of confessions and executions went on, until there was a pile of corpses lying before Napoleon’s feet and the air was heavy with the smell of blood, which had been unknown there since the expulsion of Jones.
At the end of the story, Napoleon turns into a man. The only way we can say that things got better is if we argue that animals thought things were better. Objectively things were worse.