I actually had the same thought back in high school. In my opinion there's an important difference though. Communism is forced upon you and removes freedoms. Law of consecration is voluntary--a choice you make.
Most Bishops (local leaders) will tell the family to stop paying tithes for a time or to continue to pay but then they turn around and give them food and a check for rent/mortgage until you're back on your feet. They'll work with you and frequently require that you do certain things though--like look for a job--in order to continue receiving assistance.
Communism is usually coercive, at least in the implementations we've seen, but there are plenty of theories that don't require coercion. That being said, the common usage of the term "communism" implies a dictatorship with heavy coercion.
Most Bishops (local leaders) will tell the family to stop paying tithes for a time or to continue to pay but then they turn around and give them food and a check for rent/mortgage until you're back on your feet. They'll work with you and frequently require that you do certain things though--like look for a job--in order to continue receiving assistance.