Science still can prove, one way or another, the origins of the universe with science.
This is perhaps the textbook example of how science is misunderstood. Science cannot prove how something that was not directly observed happened. It can only disprove certain proposed mechanisms based on current observation and understanding.
So, when someone says that "the CBR proves the big bang theory is correct", what they actually should say is that "the CBR is consistent with the big bang theory". I.e., the former doesn't disprove the latter.
A good analogy is found in art. I have a painting on my wall here. It looks like a Van Gogh. It is painted in the same style as other paintings that are believed to be his. A chemist has taken a paint chip and measured the properties, and found it is consistent with paint used in Van Gogh's time. Another scientist has dated the canvas and it comes from that time period. All the science data is consistent with a painting by Van Gogh.
But it isn't a Van Gogh. It's a forgery.
All I can say is, were I a God able to create a Universe from a single word, I'd certainly be able to forge it to look like it was billions of years old. Or I could just as easily create the physical laws with the knowledge of the result.
I mean, if you are designing some object to be 3D printed, are you not the creator of that object even if it takes three hours for it to print out? You told the CAD program what you wanted, and the CAD program told the printer, it just took a bit of time. That's how Algore created the Internet, after all. He didn't do the actual work, he just spoke it into existence, so to speak.