Not at all. It is we who are incomplete. We need to partake of the Sacrifice of the Cross in order to be covered by it. Exactly like the Israelites needed to eat the lamb in order to be covered when the Passover ghost came.
But since we were not all present at Calvary, historically speaking, God has given us a way to be present through the Sacrament.
If you will, the Mass is like a wormhole or singularity in time. The one-time historical event of the Crucifixion is always present in the Mass. We can always be present at the central moment in our salvation history.
The more I learn what you folks believe the more sorry I am for you. You never really know the joy of being saved. You always need your Grace refills and all the other things your church tells you that must be done.
The Truth is not that complicated.
Mark 16:16 He who believes and is baptized will be saved; but he who does not believe will be condemned.
Nothing about works, rituals or the constant refills of Grace just believe. If you truly believe you will have Faith in Jesus Alone and thru Faith Alone you will be saved by Grace Alone. It does not involve Grace refills. Once Jesus has you in his hands nothing can separate you from Him.