If God calls himself your Father, that means he is calling you his child.
That doesn’t imply you are childish.
It’s simply saying that, having brought you into existence, he cares for you and will supply your needs, much like earthly fathers do when their children are born.
Up until the time we call him Father, we often act like rebellious teenagers, rather than sons and daughters with a warm father-son or father-daughter relationship.
He desires us to receive him as Father, but that only happens when our hearts are open to do so.
Jesus expressed it well when he said –
To all who received him, to those who believed in his name, he gave the right to become children of God – children born not of natural descent, nor of human decision or a husband’s will, but born of God.