You seldom see spiritual maturity in young people. You have to walk with God a long time before you're spiritually mature and being a Christian a long time doesn't guarantee you spiritual maturity.

You need to engage in spiritual disciplines for decades. That includes daily prayer, daily Bible reading, and regular church attendance when possible. You also need to grow in obedience. I also listen to scripture based Christian music that feeds me spiritually. I also sometimes listen to Bible teaching by Dr. J. Vernon McGee from the Thru the Bible radio program. You can download the entire five year study for free at ttb.org.