The priest can’t reform your character and make you magically you unable to sin in the future, if that’s what you mean.
Scripture says “The righteous man sins seven times a day.”
Not all sins are equal as the Church rightly teaches. A stubbed toe is not as bad as broken leg, but they still hurt. Venial sins are absolved when we receive Communion.
Only mortal sins need to be confessed as they represent a break in the relationship we have with our Creator.
The Church encourages confession of venial sins. They are a weakness, a bad habit that can develop to a point where the sin being committed does become mortal.
Although he was Lutheran, and not Catholic, I recommend Dietrich Bonhoeffer’s book The Cost of Discipleship. He differentiates between cheap grace and the true cost of discipleship.
“Failure to confess sins is a sign of pride and self-deception.”
It is true that Christ died for our sins. His Sacrifice calls for a response on our part. Cheap grace means continuing in our sins. It denies the transforming power of the Cross.
Confession means absolution because as others have already stated, the priest acts
in persona of Christ. He gave them the power to loose and bind. When questioned by the Pharisees about His ability to forgive sins, a power reserved for God alone, Christ responded with physical healing.
If we in our humanity cannot confess before another human, how will we have the stamina to stand before God on judgment day? In the presence of another fallible human, we hear the words of consolation, even when our confession is less than perfect. Moreover, the confessional serves as a place of counsel and guidance. How can I repair the damage my sin has caused? More importantly, what can I do to change my life, to change the habit that caused the rift, or in the process of creating a rift between me and my God? If there are other members of the Body of Christ involved, what can I do to repair the relationship that has been damaged?
The priest does not change me into a good person. I am the only person with that power, and then only through the transforming grace of God. The priest is available in my need, even as Simon the Cyrene was available to help carry the cross on Calvary. What I need is the Sacrament and healing that comes only from God through His minister, through the man He has called for that purpose.