I think perhaps the best thing you can do to understand the Catholic position on the mass is read the Liturgy of the Eucharist… the prayers and assertions made by the celebrant, to understand what is being offered to the Father, and why. The best I can do is summarize for you what our belief is:
(1) Adam’s sin separated all of us from the Father. Without a restoration of that unity with God, no one can go to the Father in Heaven.
(2) Because Adam’s sin offended God who is infinite, only a sacrifice of infinite worth can redeem for that sin.
(3) Christ was that infinite sacrifice - at Calvary. His submission to the will of the Father by: (a) taking on a human nature and; (b) giving up His own life in obedience to the will of the Father, was the only sacrifice that could restore man’s relationship with the Father.
(4) Before He went to His death, Jesus told his followers to take bread and wine, bless it and share it… that it was His Body and Blood of the new covenant.
(5) Jesus also said He was the Bread of Life, come down from Heaven, and that if we did not eat His body and drink His blood we would not have eternal life…
and so at the mass, we do what He told us to do. Don’t take my word for it. Read for yourself:
Here
The mass is offered because we believe Jesus’ words that we must eat his flesh and drink his blood. We offer the mass because he asked us to do it as a remembrance of Him. And we do it because it re-presents that one infinite sacrifice to God in a real and tangible way in which we participate in its benefits, through receiving the real body and blood of Christ made present under the appearance of bread and wine.
Peace,
Robert