The lamb was the ultimate sacrifice, yet G-d made man master over the animals. How then can this alone bring redemption to man? Is it not a symbol of something greater than us to be sacrificed?
An animal sacrifice is a representation of the idea that a man offers himself to G-d, but G-d does not require or desire that the man offer himself in death. Rather, he offers himself by living a holy life. However, we recognize that our failures might be grounds for serious punishment, so G-d allows us a symbolic sacrifice of our property, which is an extension of ourselves, with the idea that in a sense I should really be sacrificing myself. Today, prayer and giving charity provide a form of substitute for the sacrifice.