Had to reply even if the topic is so old.
The "no true communism" or "no true socialism" arguments don't really see what Animal Farm wants to tell the reader. There always will be a power hungry group that will use all means necessary to grab and hold onto power. The idealism portrayed by snowball has no chance in a system, that is so easy to overthrow by concentrating power. Communism and Socialism will always end up with a totalitarian leader, there is no defense mechanism.
In a democratic and capitalistic society political power and monetary power are divided. Capitalism can flourish in many different variations of democracies and is an outlet for power hungry people and groups to do something, that might even benefit society. While people who pursue political power can decide how to distribute the wealth (in Europe more is distributed in the US less).
It's not a perfect system, but it is by far more resilient against totalitarian regimes. It kept the balance for centuries in some states while communism and socialism can't even really form before a Dictator takes over.