Would you say the same about an adaptation of The Lord of the Rings where Frodo is not a hobbit?
Actually asking, not rhetorical.
Well, since you mentioned hobbits...
Steve Bein said it more concisely than I could have in the author's note in Daughter of the Sword:
There is a scene in the film adaptation of The Fellowship of the Ring that got the attention of some vociferous critics with a lot of time on their hands. The four hobbits sit around their campfire on Amon Sȗl cooking a dinner of tomatoes, sausages, and nice, crispy bacon. The critics complained that tomatoes are a New World food, and that it is therefore unrealistic for hobbits to be eating them. This sort of complaint tickles me. Four hobbits travel in the company of a ranger still in the prime of life at eighty-seven years old, they search for a wizard on a hill with an Elvish name, they are soon to be attacked by deathless wraiths, and what's unrealistic about this scene is that they're eating tomatoes.
Mostly tangential to the argument: While I agree that bothering to consider whether tomatoes would exist in Middle-Earth is pedantic, I've never been fond of the "The story has [fantastic element] and [mundane mistake] is what bothers you?" argument. The general assumption of any story with fantasy elements is that it diverges partially from reality, but on the things that it has explicitly stated so, and the rest is standard. If I'm reading a fantasy novel and the characters speak English, then I assume all the words mean the same until the book states otherwise. If the book has human characters, I assume their biology is the same as real humans, unless the book explicitly states they have naturally-occurring red eyes or something, and then all non-red-eyes parts are human standard.
So then when I complain e.g. that one character's pregnancy could not have have come to term in the time the book says it did, saying "these people have magical powers and you're worried about four-month pregnancy" is stupid, because four-month pregnancies are not part of the deliberate fantasy elements introduced by the book; it's an actual author mistake.
What does that have to do with anything? Very little, I just felt like ranting. Though I will observe that changing the race of Moses is no the same kind of unrealism as turning staves into snakes or parting the sea, because once again, those are the explicit fantasy "God did magic here" parts of the story, whereas it's not really part of the story that God changed Moses' race, it's just convenient casting.
The problem is never the degree of unrealism. The problem is whether the story embraces that unrealism as part of the things it has decided "yes, I'm making shit up here" vs the parts that are presumably the same as the real world.
Of course, this is all complicated by the fact that according to the Bible, nothing is in the former category. But if you're gonna take Exodus as a story rather than history then I think the dividing line is pretty clear.
