The finality of Christ’s atonement undermines the claims of any other mediator, be it temple, priesthood, and even church. Other mediators leave people conscious stricken. Christ leaves our consciences clean.
So, why are the consciences of many Christians still guilt-ridden?
First, because some may not yet be regenerated. Their religion is akin to “having a form of godliness but denying its power” (2 Tim. 3:5). Preach the atonement and imputed righteousness to such as these (see “Why Rite 1?” nearby).
Second, Christians who are truly born again can still find their consciences pricked by sins past and present. But this is different than the guilt the unregenerate man or woman experiences. The reprobate man suffers from ignorance. The saint suffers from frustration, groaning inwardly as the Spirit works out all of the implications of salvation in his life (Rom. 8:18-23).
This can hurt, the way a fever spikes when the virus dies off. The stricken conscience of a believer means the old Adam is dying. Good riddance.