The very concept of sin has been blunted and blurred by decades of psychological conditioning by atheistic and humanist educationalists of every kind. We are beginning to reap the sad and painful reward for that folly. It doesn't exist says a generation of hedonists. There is no sin, morality, no God and no fearsome judgment to come. He has in the clearest terms defined sin.
Sin goes deep.
Every ill that assaults mankind results from it. And unless that sin is dealt with in God's prescribed way the end result is a waiting for fiery judgment. So - not just the act of adultery, but the imagery, the thoughts, the preparations which lead to the act. And not just idolatry , bowing before and image, but worshipping God at a time and in a manner He has not prescribed. Whether or not you see yourself as a sinner doesn't affect the result.