If we try to understand A by saying 'B must have made it', this gets us nowhere if we cannot say where B came from. The creator fallacy is thus a false friend - appearing to solve a problem but in fact it only invites an infinite regress of creators which is a more intractable problem than just understanding A. Another way to think of it is as a painkiller - it doesn't really address the underlying problem but it makes the pain go away.
I don't think anybody is saying 'must'. I think most theists respect that there are other thought solutions to the great question but that at the end these are themselves unfalsifiable.
Infinite regress is one hazard of having big bangs and...it looks as though we have one and that invites an infinite regress which doesn't seem too problematical for you (special pleading?).
We are both, in our thinking, after an overall solution to the big question. If you are saying there is one.....How is that different from a God proposed solution?(more special pleading?).
Then we don't have even to consider a regression of creators or big bangs do we?
All we have to do is either have an infinite God or an infinite unconscious universe....and you won't accept the former why?(special pleading?).
Your beef really seems to be with a conscious infinite and that is pure naturalism.
Penultimately, those who realise that there is, contrary to what you say, no ''must'' about it. Have you not contemplated that these peoples actual belief in God is contingent on other things...not least an experience of God?
However this is more about you and IMHO you and your like accept philosophical naturalism all too readily and are too certain that it possesses some kind of flawlessness.
Finally there are Christians who are agnostic about God the creator and others like Origen for whom pre-existing matter is not a problem. They would say that this is because they are followers of the living Christ.