So goes a common argument leveled against faith in Jesus by many apologists for rabbinic Judaism. If it is, then Christians cannot claim that their sins are forgiven because of their faith in Jesus' death. It would mean that only unintentional sins are covered by Jesus' death. The issue of blood atonement is a crucial one in both Judaism and Christianity. There must be a sacrificial death.
Blood is the sign of death.
As a matter of fact, it is the death which brings atonement, for the mere bleeding of a victim is not sufficient. The victim must die as a sacrifice. The victim's death is a substitution for the death of the offerer. The sacrifice must be considered sufficient by the one it is being offered to, usually a deity. Various rules apply regarding what types of sacrifices are sufficient and which are not.