Pax Christi Dino!
About a year ago, I had actually asked similar questions about The Exodus, which I had taken at face value and completely for granted up until that point. I did some looking into it for a while, and it seems safe to say that while a horde of millions (who could have easily overrun their Egyptian assailants and fertilized the desert) is not historically accurate, there are still good reasons to take the narrative seriously.
There’s some quibbling one could get into regarding why the number of Israelites is so large; some might say that the Hebrew speaks only of clans yet gets translated into millions, while others such as Richard Elliott Friedman might say that the high number was intentionally done to retroject the then-current population of Israelites into the story of the few involved in the event (The Levites, everyone else was indigenous Canaanite) so that The Exodus could be the story of everyone, and there are those like Dr. David Falk who posit that the Hebrew speaks of perhaps hundreds or tens of thousands. So while we struggle to find evidence of an Israelite group in the millions, it is unlikely that such a central and embarrassing origin myth would have just been made up out of thin air and not have a basis, especially since it has connections to the Egyptian named Levites, involves God who was first called YHW in the significant land of Midian, Pithom and Rameses and their Semitic populations, the war tent of King Rameses, birthing bricks (as weird as it sounds), the Merneptah Stele and its mentioning of Israel as a people group and not an established nation, and a bunch of other stuff that I’m probably forgetting.
With all that being said, we can think about this Christological issue several ways. First and foremost, it is important to remember that God came down to the 1st century Roman world as a 1st century Jew, so He had to have been able to communicate with everyone by using things they already understood, regardless of its accuracy or not; He calls the Pentateuch the Books of Moses, never mind the multiple authors involved in its gradual making or the lack of any assertion of Mosaic authorship, but that was how His audience knew it.
At the same time, if The Exodus had no such basis in reality, I suppose it could still be somewhat inspiring, but not only would all of the significance be lost, but it would mean that God never called anybody out of Egypt.
