You can understand Catholicism (and the errors of Protestantism) much better if you simply understand one fact: God wants his children to join with him in his good work whenever possible. Thus he has made it such that we join with him in bringing forth physical life, and we join with him in bringing forth spiritual life (baptism and the other sacraments), and we join with him in spreading knowledge of his gospel, and we join with him in making present his one sacrifice throughout time and location.
Seen in this light, confession to a priest is not a burden, as so many think, but rather another gift of God to his children. He invites them to join with him in the forgiveness of sin, which is a tremendously good work, everyone would agree.
Of course like any father, God can and will take care of matters himself if need be. He never needs our assistance. But his wish is that we join with him in this whenever and wherever possible, because his nature is to share all that is good with those whom he loves.
BTW, this also applies to angels. God certainly doesn’t need angels to do his bidding. Rather, he grants them the wonderful gift of joining with him in bringing about his will.
It’s all quite wonderful when you think about it.