Origin, you miss the point by dissecting posts. Every comment becomes a discussion out of context.
Theories are no longer theories, once they are proven.
The tendency to discuss theory as fact has a long record and is not limited to any individual, or credentials. The specific quote that triggered my attempt at reminder of the difference between what is known as a matter of fact and what remains the subject of theory was,
No, as I have said we do not have the ability currently to know anything about the universe before $$10^{-43}$$ seconds.
I read the above, perhaps incorrectly as implying that we do know with certainty what happened after the initial $$10^{-43}$$ seconds, of the Big Bang. Theoretically yes. With certainty no.
Mark this one up to my current favorite complaint. I read as many research papers as I can these days. I am retired and have the time, most of the time. Most often credible papers make it clear that they are presenting a theory or their theory and often even point out their own flaws. By contrast in discussion groups theories are often described as if they were settled fact, rather than our best explanations.
I never really meant anything personal, but an example as you requested, might be general relativity. While it has been very successful and many predictions have been proven, the theory remains a theory and as a whole is yet to be raised beyond the level of theory.
The standard model of particle physics has been one of our great theoretical achievements and yet at very high energy levels it begins to return unreasonable results and predictions.
The big bang remains a theory with less experimental confirmation than either of the above. And yes it does fit observation well... But then we human beings have always been good at finding believable explanatintions that fit what we see, very nicely, until we discover things work differently than we thought.
As I mentioned earlier, I would say I am an agnostic as to what the beginning, if there was a beginning looked like..., way to long before my time.
I will say that I believe it is likely that both GR and what we currently know of QM will both look very different in another few hundred years. Even though they are our best descriptions and explanations of what and how we see the world today.