"Christ becomes wholly and really present under the forms of bread and wine, and He is offered to God by the Catholic priest for the remission of sins, by means of eating the Host (Christ's body) and drinking the Wine (Christ's blood). This doctrine is strongly reflected in that part of the Pre-Vatican II Tridentine Mass called the Offertory, where the Priest offers the bread (the Host or "hostia", meaning "victim") with the following prayer: "Receive...almighty and everlasting God, this spotless Host, which I thine unworthy servant now offer unto thee... for my countless sins, wickedness and neglect; and for all those here present, as also for all the faithful in Christ, both the quick and the dead, that it may set forward their salvation and mine, unto life everlasting. Amen." He likewise offers the wine using similar language." Wikipedia
The human Priest cannot 1) Offer up our Lord as a sacrifice-He already did that Himself on the Cross. 2) He cannot intervene on our behalf-your salvation is between you & God alone 3) The "quick and the dead" means the living and the dead.
During the Reformation Luther opposed the Mass because - "What he objects to is the claim that Christ is at our disposal to be made into an object that can be presented to God in order to gain his favors. It is that which damages both the sovereignty of Christ and the complete character of his work on the cross." Issues,etc. Luther and the Mass
We already have a High Priest in Heaven ministering on our behalf. Seeing then that we have a great high priest, that is passed into the heavens, Jesus the Son of God, let us hold fast our profession. Hebrews 4:14 We have such an high priest, who is set on the right hand of the throne of the Majesty in the heavens; Hebrews 8:1