Someone may own a nice leather Bible and not read a word of it.
Someone can take notes on every sermon they hear and not do anything the preacher says.
Someone can attend a Sunday worship program and never actually worship God.
Someone can be a member of a Church and not be growing spiritually.
All of those things are excellent tools that can be used to become more like Jesus, but one does not guarantee the other. Someone can have the best tools and be a part of a fantastic Church and still be a spiritual infant.
The only thing I know that is required for someone to become a mature believer is desire. If you desire to follow Jesus more closely, nothing can hold you back. If you don’t desire a close relationship with Jesus, even the best tools can’t help you.