If we go strictly by what is revealed in the Bible then "really".
1. The penalty for sin is death. Which includes both the first death (physical) and the second death (eternal separation from God in the Lake of Fire).
2. Either all sinners must die both deaths, or a substitute must be provided whose blood must be shed to *atone* for sins.
3. The blood of animals shed under the Old Covenant was only able to *cover* sins. Hence the Hebrew word
kaphar is used and translated as *atonement*. Therefore there were daily, periodic, and annual sacrifices required under the Old Covenant.
4. But the blood of Christ -- called "the blood of God" -- has infinite value not only to take away our sins, but to wash and cleanse our souls, so that the defilement and guilt of sins are removed at the same time as our sins are forgiven.
5. However, there was more than the blood being shed. The sufferings of Christ during His passion, as well as the offering up of Himself -- body, soul, and spirit -- was the total sacrifice which replaced all previous sacrifices. "He made His soul and offering for sin".
6. When Christ suffered on the Cross during those three dark hours, He literally bore the wrath of God against all sins and all evils upon Himself. Hence "My God, My God, why hast thou forsaken me?"
The theological terms are "penal substiutionary atonement" but for those who want the simple truth, John the Baptizer said "Behold the Lamb of God which TAKETH AWAY the sin of the world" (John 1:29).
So anyone who denies these truths falsifies the Gospel.