Animal sacrifice is the ritual killing of an animal. It is practiced by many religions as a way to appease a god and gain forgiveness for a sin and/or as a bribe to a god so that various favors will be granted.
Cruel and wasteful behaviour of God
God ordering the sacrifice of animals is cruel and a needless waste. Such a God is The scriptural God is unworthy of worship.
The rituals that call for animal sacrifice are based on religious motivations that are generally fictional. There is no good reason to sacrifice animals to an imaginary entity.