Well, it helps me to see things better from a Roman Catholic point of view.
Still, it doesn't really answer (for me, anyway) the question of why Jesus, if He intended -- or commanded -- that sins (or even a certain category of sins) be confessed through a priest to God, would respond to a request from His own disciples about the proper way to pray, and include in that prayer -- a prayer prayed directly to "Our Father" -- a request to have one's trespasses (or debts) forgiven.
Why, if Jesus commanded His followers to confess their (mortal) sins to God through someone else, would Jesus have included this specific petition -- prayed directly to "Our Father"?
Jesus could have prayed like this, when demonstrating the way to pray to His disciples: "Provide us a means for the forgiveness of our mortal sins", but that isn't what he says.
He seems to make a point, in this prayer He prays in response to His disciples' request for a demonstration of prayer, of demonstrating that the sinner may -- or should -- request his or her forgiveness directly from the Father.
Don't go overboard weighing one passage against the other. Each finds meaning in the other. And consider that all Churches before the 1500s taught that God's forgiveness is normatively found within the context of John 20, as the Catholic Church teaches to this day.