Not only the big bang but also burning stars. But those conclusions are derived from strong physical evidence. Your intention appears to pretend that they're nonsense, to justify more outlandish ancient misconceptions of the world. Miraculous creation by imaginary sky beings, for instance. Where your ancient authors "there"? What evidence do you have of that? A claim that they made in a book? Also, "chemicals" are always non-living. Biology is more than just "chemicals", even if it's not magic.
It's possible that this was a theistic evolutionist argument, because it only touches the big bang and abiogenesis, apparently. But evolution is often confused with those by creationists as well.
There sure are gaps of knowledge in science, it does not make science non-science. Gods of the gaps are however not only inserted where scientific knowledge is limited, but anywhere a person's own ignorance allows. What "ignited" the big bang is much more mysterious than how it happened and how elements and planets formed, which is much better understood. How life evolved is much more understood than how abiogenesis occurred too. There's progress being done to understand abiogenesis, but it's far from solved.
Does it make science non-science? That argument is basically, if science doesn't know everything it's not science, which is ridiculous. Or the argument of "theistic science": forbidden to explore where modern human interpretation of old human mythology dictated, taboo, which will not satisfy the inquisitive. A version of this claims that science is only useful for technology and should not be used to investigate the past, a form of denial that it can use reliable means and strong inference to do so. All of these amount to censorship to dictate mythology instead.
Hypotheses are also part of science. Its working scientific theories rest on many working hypotheses and a lot of evidence. And at least the scientific method attempts to deal with human fallacies, to hopefully distinguish the real from the scientist's fantasies. It's universal too, not one of many conflicting sects claiming to have the ultimate truth. Anybody qualified can participate to improve it.
Various excellent comments above, a joy to read.