Big Bang cosmology remains viable because its effects are not dependent on knowing a specific cause. In other words, we can be unaware of the cause, but we can still observe the effects.
But the effects are not in question. No one has doubts about the effects. We can observe them. The key question, though, is "what best explains those effects?" The answer, "gravitational fields" is totally inadequate to the observable effects.
It is the best answer we got in terms of a theological and metaphysical explanation, but as a scientific explanation it is pseudo-science.
What makes the best answer "pseudo-science"? I thought "best answer" was precisely what science seeks out. You cannot dismiss a First Cause simply because you don't like what it entails -- or rather, you can do so, as anyone can: but not and be a rational person. To do so is not scientific but gratuitous.
"God of the gaps" is a theological perspective
Oh yes...I know all about that. Nobody but Deists and the philosophically naive believe in it though, so it's totally a straw man here. Theism does not require a "God of the Gaps" explanation. It's not just philosophically but also metaphysically absurd as a view.
And in saying so, I'm not invoking the "No True Scotsman" fallacy. There are good reasons for dismissing it. Consider, for example, that if God is only a God of gaps, then every time a gap is closed it is discovered that the phenomenon in question was
not actually God at all. ( This is precisely the point of the God-of-the-Gaps criticism). But then it wasn't really a
Theistic view at all either.
Theism can, and does, posit a God capable of generating natural laws and allowing human freedom to operate within those laws or predictable realities, rather than one only capable of micromanaging the universe and reducing human freedom to a mere illusion.
Thus, if a particular phenomenon is scientifically discovered to be due to a law rather than direct Divine intervention, the Theist is not surprised. He can simply respond, "Yes, that's what we'd expect from a law-giving God." Having no "gaps" in natural explanations, such as those posited by the God-of-the-Gaps critique, he isn't put off by one being closed. It's what he'd expect.