Did the blood of bulls take away their sins? No. Did their faith in God to forgive through genuine faith and repentance take away their sins? Ultimately, yes

Animal sacrifice is a reminder of sin and during the millennium will be a memorial to the sacrifice Jesus made on the cross. Once the age of grace ends the age of law will be reinstated and animal sacrifice is part of that dispensation....also it gives the earthly high priest dominion on earth fulfilling the genesis 1:28 covenant.