The biblical tradition has never treated youth as a waiting room for adulthood.
Samuel was a child when he first heard God’s voice calling in the night. He didn’t recognize it at first, kept running to the priest Eli. But God was not waiting until Samuel was older or more qualified.
David was a young shepherd, the youngest of his brothers and the last one anyone would have picked, when Samuel anointed him king. Nobody saw it coming. That was apparently the point.
Mary was likely a teenager when the angel appeared with news that would change the world. She didn’t ask for time to grow into the calling. She simply said yes.
Jesus was twelve when he slipped away to sit with the temple teachers, asking questions that left the adults lost for answers.
The pattern is hard to miss: being young has never once stopped God from calling!