But, you are correct, "the blood", the sacrifice Jesus made covers our sins. I have never met a brother or a sister that doesn't believe that.
The value of the blood covering is ONLY accessible through the New Covenant - Read it again:
And taking a cup, he offered thanks and gave it to them, saying: “Drink out of it, all of you, for this means my ‘blood of the covenant,’ which is to be poured out in behalf of many for forgiveness of sins.
JW's live a life of total rebellion against the authority of Christ. There is simply no way to apply the blood covering without entering into this agreement. Many people (not just JW's) have made the mistake of going through their church affiliation (or some other way) to get access. But a person must do business directly with Jesus.
Verily, verily, I say unto you, He that entereth not by the door into the sheepfold, but climbeth up some other way, the same is a thief and a robber......I am the door: by me if any man enter in, he shall be saved - John 10
Now if any man have not the Spirit of Christ, he is NONE of his.” - Roman 8: 9
It is a complete deception that imagines that a person can be friends with Jesus by disobeying his commands to get their sins forgiven as prescribed in Mt. 26: 27-28