That’s tautological. We observe the effects, and assume they must propagate backwards under rules we think we know, then say that the theory must be true because we observe the current state is the forward propagation under those same assumed rules. It’s unfalsifiable and accordingly uninteresting.
The reason why we assume the same rules is because 1) we haven't observed anything that implies that they changed, and 2) if we assume that they did change, then any attempt to figure out what really happened is moot anyway.
From a religious perspective, there's a take in e.g. some mainstream Islamic madhabs that time is an illusion that is caused by God literally recreating the entire universe moment after moment. He just happens to do so mostly in a way that is consistent with stable laws of nature, but ultimately it happens that way because God wills it to happen that way and for no other reason - there are no actual laws. If you adopt this viewpoint, then for all you know, the universe can be literally one second old, and all your memories of past events are just pre-created. That is unfalsifiable and uninteresting; the assumption that there are stable laws that hold, to the contrary, is interesting because it allows us to make interesting conclusions that also turn out to be practically useful in some cases.
We’ve been making detailed observations about a system in a sort of “steady state” for ~100 years and have the hubris to imagine that steadiness carries back 100,000,000 times as long as the observation period, all the way through the start state, into the origin. It boggles the mind.
And yes, any attempt to figure out what happened is moot. As you detail in your second paragraph. I don’t think much of it one way or the other, besides to interject when someone makes any sort of claim that “the science” points to their particular faith’s origin story.
Can you give an example of any of the practical use cases for the Big Bang origin story?
It would be silly to assume that the criteria that yields a law (or a system) be itself subject to that law or system. Logically, that criteria must encompass the system and cannot at all be subject to it
