because there aren't any talking animals

Biologically speaking humans are animals and we talk. And since evolution resulted in one type of animal that talks couldn't it result in others, maybe even other that have since gone extinct? So there has to be an additional reason to dismiss the story other than talking animals being rationally impossible. You mention that the problem is the "magical" causation, which you see as a synonym for supernatural, whereas in Christian Theology it is closer to an antonym.

So let me tell you a story I made up:

Thahg and Zog are aliens in a faraway solar system study species of other planets. One day Thahg shows a pocket watch to Zog and says "Look, I think a human made this." Zog says, "What's a human?" "A human is a featherless biped from Earth" Zog thinks about what animals come from earth and the only one he can think of is a chicken. He laughs and says, "You think a plucked chicken made that? Boy, are you nuts!"

And of course Thahg would then look at Zog like he was nuts, because the absurdity Zog is seeing is coming from Zog's own lack of appropriate reference categories rather than an actual problem with Thahg's conjecture.

For another example suppose the Muslim woman Yvain was talking to had said "I don't believe that evolution could work because alleles that sweep through populations more often then not reduce the kolmogorov complexity of the genes' effect on phenotype." Yvain may still think she is just as wrong, but she has demonstrated intellectual engagement with the subject rather then just demonstrating she had no mental concept for genetic change over time, like the 'monkeys give birth to humans' objection demonstrates.

So the problem is saying that talking snakes are magical and therefore ridiculous sound more like "My mental concepts are too limited to comprehend your explanation" than like "I understood your explanation and it has X, Y and Z logical problems."

But, the usual story isn't that it was created by technological means, but by supernatural means.

I hope you're familiar with Clarke's Third Law?

Pretty much every variation on a religion you can think of has been thought up by someone, at some time in the past. You can't use that as your criteria for "ancient tradition" without making the whole concept of "ancient tradition" meaningless because now everything is one. How mainstream was the belief that Genesis is not literal?

For that matter, since religion is supposed to provide eternal truth, the idea of having a minority tradition in sometinng seems problematic. If a religion has multiple traditions at once, how do you decide which one counts as the "real" one that nonbelievers should be criticizing? And if the ancients had beliefs A or B, but moderns only have A, how do you decide that that counts as the ancients believing A (so you can claim that moderns are following tradition) rather than as the ancients believing B (which means that moderns are breaking with tradition)?

The attitude of science to its past and the attitude of Christianity to its past are very (and relevantly) different.

In science, everything is meant to be revisable in the light of new evidence; authority is always supposed to be subordinate to reason and experimental results; there's a reason why the motto of the Royal Society is nullius in verba.

Christianity, on the other hand, has authorities up the wazoo. (Different authorities for different sects.) The Bible (held by many to be perfectly free from error). The Magisterium of the Roman Catholic Church (held by many to be perfectly free from error, subject to certain conditions). The ancient creeds (held by many to be perfectly free from error). The Thirty-Nine Articles of the Anglican Church. The Apostolic Fathers. Luther. Calvin. Aquinas. Augustine. Accepted as authorities (in so far as each one is, by any given Christian) not in the way that someone might appeal to, say, Murray Gell-Mann ("he's incredibly smart and has been very reliably right before -- but of course whatever he says can be checked by other people and anyone can make mistakes") but simply because they're Known Authorities.

In science, a discovery from 200 years ago may be admired as an impressive piece of work, but the assumption is usually that since then we've improved our techniques, done more careful analysis, and superseded it.

In Christianity, all the central ideas are centuries old, they are explicitly passed down the generations, and they are believed largely because there is a tradition (etymology: a thing handed down) saying that one should believe them -- and, in many cases, because it is thought that they originally -- centuries ago -- entered the world at the command of God.

The best reason for accepting any given scientific theory is generally that there is good experimental evidence that it describes the world accurately. In principle, anyone -- at least anyone with the right skills and equipment -- can repeat the experiments and redo the mathematical analysis and arrive at the same conclusions. (Or, in some cases, arrive at different conclusions and show that everyone's been wrong.)

The best reason for accepting the central doctrines of Christianity is that there is a ~2000-year history of other Christians accepting those doctrines and believing that they derive from the all-knowing all-good creator of the universe.

(Of course the above is a bit too black-and-white. In practice most scientists believe a lot of what they do because they heard it from other scientists whose judgement they trust. Some Christians believe some of what they believe because it just feels right to them, or because they consider that God told them directly. But the difference I describe is there and it's a big deal.)

So, if it turns out that until 200 years ago all the scientists were wrong about something important, we should re-check any bits of their work that we're still depending on, but science is a largely self-correcting enterprise and it's probably no big deal. And our scientific opinions now are not supposed to -- and generally genuinely don't -- depend on the judgement, or the character, or the rightness-about-any-particular-issue, of those scientists 200 years ago and more.

But if it turns out that until 200 years ago all the Christians were wrong about something important, it's a really big deal. Because so much of what defines Christianity is what Christians of past ages have handed down, and because so often the case for believing X is something like "all the earliest Christians believed X".

It would indeed, if it said that. The page you linked plainly doesn't.

It's not impossible conditional on the existence of strong magic. I'm not so sure it's not still ridiculous even conditional on the existence of strong magic. Especially as, in the story, the snake doesn't appear to be magically talking, it's just "more cunning than any of the other creatures YHWH had made" or whatever exactly the text says.

We now know that talking requires a big fancy brain, such as humans have and snakes conspicuously don't (and don't have room for), and the right sort of vocal apparatus, ditto. Back in 2000BCE or whenever it was, of course it was well known by observation that snakes don't talk, but it presumably wasn't understood that they can't and why. And when we see an old story featuring a talking snake, which doesn't present it as able to talk on account of some sort of magic or divine intervention but just oh, hey, a talking snake, I think it's reasonable to say to ourselves "See, the people who wrote that story just didn't understand how implausible that bit of it is". And I think it's reasonable to see the talking snake as making the story less plausible than it would have been without it. And also, I think, less plausible than if its talking had been explicitly explained by magic or divine/diabolical intervention. Not because those are plausible explanations otherwise, but because the rest of the story is already committed to the sort of world in which such things might work, and in such a world a magically or divinely talking sheep is more plausible than an "ordinarily" talking sheep.