Then they try to confuse the issue by claiming that modern Christians don't need to be part of the New Covenant "for the forgiveness of sins" (See Mt. 26: 27-28)
And this is what it is all about. It is an excuse to reject the NC every Lord's Supper so that JW's CANNOT be saved by virture of Christ's blood.... which is the offer on the table for church-age believers.
If I'm following you correctly, the point of the WT is to prevent witnesses from eating and drinking at the Lord's supper.
Altho this is certainly accomplished in a literal way, sincere jws are still choosing the side of Christ. Meaning, those that truly have faith in the general 'life saving' message.
It doesn't seem plausible that God would punish a person who has chosen correctly in their heart on account of following incorrect directions. That seems to be placing more importance on the ritual than the principal itself.