In his commentary on "salvation" in Romans 1:16, Barth says
...our desire to comprehend the world in its relation to God, must proceed either from the criminal arrogance of religion or from that final apprehension of truth which lies beyond birth and death - the perception in other words, which proceeds from God outwards. When the problem is formulated thus, it is evident that, just as genuine coins are open to suspicion so long as false coins are in circulation, so the perception which proceeds outwards from God cannot have free course until the arrogance of religion be done away.Karl Barth, The Epistle to the Romans, 6th Edition, page 37
Religion is man seeking to find God and earn favour with God through his own efforts and wisdom. The Gospel is God reaching out to wretched humans who have nothing to be proud of.