In the following visual addendum to the sermon, Excretion: Getting Rid of the Junk (6 of 7), I talk about why repentance is absolutely necessary for being a disciple of Jesus.
Also, check out this post by Roger Olson on why we can't appeal to Nones (religiously unaffiliated) and Millennials by holding off or omitting the need to repent of our sins.
“Repent and be baptized, every one of you, in the name of Jesus Christ for the forgiveness of your sins. And you will receive the gift of the Holy Spirit." Acts 2:38 NIV