If you think the Bible is childish, then I can only assume you've never studied it in earnest. These aren't fairy tales. They are a collection of books written in numerous styles and languages belonging to various genres drawn from many cultural contexts spanning thousands of years and whose canon was determined by the Catholic Church in the 4th century (most famously, at the Council of Rome when the 73 books were listed). Theologians, philosophers, and biblical scholars are deepening their understanding of this text to this day.
Just look at something like John 1:1: «In the beginning was the Word, and the Word was with God, and the Word was God.» Most adults aren't in a position to comprehend that, never mind a child. It is one of the most profound sentences ever uttered (those with sufficient philosophical and theological background might find this recent book on this topic of interest [0]). Or consider Exodus 3:14: «God said to Moses, “I am who I am.” And he said, “Say this to the people of Israel: ‘I am has sent me to you.’”». If that doesn't knock you off your feet, then you have not understood it. This is an incredibly sophisticated metaphysical statement, the meaning of which was unknown to the ancient pagans. (A good, short introduction from a philosophical angle can be found here [1].)
But more importantly, both you and the author of that article have committed a very basic category mistake. The Bible is not in the same business as the physical sciences. It doesn't answer the same questions. The Bible is not a scientific treatise, and the physical science are not a path to salvation from sin.
The Bible is also not a text of mere parables and life lessons. Indeed, this is one of those distinguishing features of Christianity that many fail to appreciate. In other religious traditions, it doesn't really matter where the truth claims come from or who said them. You could accept the claims without knowing or caring about the author. But you cannot do that with the figure of Christ. You cannot say "Oh, I accept the lessons of the New Testament, I think Jesus was a wise teacher. I just don't accept his divinity or the resurrection or the miracles or all that other stuff my bourgeois sensibilities can't stomach." Those claims that are uniquely Christian are about Christ and rooted in the authority of Christ. It is Christ who saves - a person - not knowledge, not some method, not a technology, but a person. Christ calls himself the Alpha and the Omega, the beginning and the end of all creation, eternal, the Almighty, and the source and completion of history and salvation.
That's not just some "fun" or "cute" passage. The point is that - if Christianity is true - it is through Christ that Man's relationship to God is restored and elevated. It is through Christ that man is ennobled. Man is invited to participate in his divinity, and unlike other traditions that maintain Man can attain divinity through his own efforts alone, the Christian says "no", it is not in Man's power to do that, to pull himself up by his own bootstraps; only God can do that, and the way is by answering "yes" to his offer, by cooperating with him so he can accomplish that divinity in us. To do that, God humbled himself through the Incarnation to share in our humanity: «the Word became flesh and dwelt among us». He entered the pathology and disorder of the world to liberate it from it, to be the path out of it.
That is what Christianity teaches. That is what Christmas is about. Either that is true, or Jesus was a liar or a madman. What he wasn't was merely another "wise teacher". Either Christmas celebrates this momentous historical event of the Incarnation, or it is ridiculous.
[0] https://a.co/d/1QtQWCP
[1] https://a.co/d/bSqgkXq