Hi and thanks for asking.
“It is finished” refers specifically to the Mission of Christ as Redeemer. He affirmed that the precise reason for His Incarntion [God becomming also man] was to once again make Redemption both complete and POSSIBLE .
Because of the sins of Adam and Eve, access to heaven had been blocked as the primary consequence of there sin.
Those early souls found to be worthy of salvation had to wait in a place without pain or suffering’ BUT also without the GLORY of actually being in the Divine Presence, until Christ, "the New Adam, reopened the gates of heaven.
“As by one man’s sin they were closed [LOCKED], so too, by One man’s Sacrifie, [Jesus] the access to haven again bcame possible.” There ad then the precise mission of Christ was now “fulfilled.”
The Catecheim: # 1382 “The Mass is at the same time, and inseparably, the sacrificial memorial in which the sacrifice of the cross is perpetuated and the sacred banquet of communion with the Lord’s body and blood. But the celebration of the Eucharistic sacrifice is wholly directed toward the intimate union of the faithful with Christ through communion. To receive communion is to receive Christ himself who has offered himself for us”
In a profound way the Mass is at one an the same time, inseperately an fully:
A Sacrifice Sacrament
A Consumption Sacrament [Presence Sacrament]
A Worship Sacrament
This explains the primary purpose for the Mass.
Mass is always to be FIRST; GOD centered Worship.
Mass first and foremost is a “re-presentation”
NOT a Representation, but a making the Sacrifice of Christ present time and time again. “Do this in memory of Me.” Are the words of Institution by Jesus of the Priesthood, and priest are absolutely essential to “making” Christ Present in the Eucharist.
The words of Consecration are: “THIS IS MY BODY” and "THIS IS MY BLOOD."
While Eucharist requires the intercession of the priest; nevertheless, it is actually brought about by God. Eucharist is From God, of God and primarily for God; and yet only we actually benefit from it. God being perfect cannot become "more perfect."
The term applied to this DUAL miracle is:
"Transubstanuation" and it involves two back to back miracles.
**At the words of Consecration: “This is…” **the priest is actually changed into the “person of Jesus Christ” [which is the main, but not only reason, priest MUST BE male gender]…The priest for the instant of Consecration become “alter Christi,” “another Christ.” Thus it is God who also makes His Divine Glorified, Body, Blood, Soul an Divinity Present. It is an UNBLOODY sacrifice, because Christ can “die” only once; and yet; it REALLY IS THE SAME JESUS BORN OF MARY, THE SAME JESUS WHO DIED ON THE CROSS that we receive in Catholic Holy Communion.
The first reason for this Sacrament, [Sacrifice to God] leads directly into the second reason. The consumption of the Real Jesus as the most perfect and plentiful source of Redemptive - GRACE needed for human salvation.
The second reason ought naturally lead to the Third reason; Divine Worship outside of the Mass.
Next to actually receiving Jesus Himself in Catholic Holy Communion, Eucharistic Adoration is the next “best” source of Divine Grace. Everyone ought to avail themselves of time in front of the “Real Presence” reserved in the Tabernacles in our Churches.
Love and prayers,
Pat