It is the only valid theory at this juncture on the question where everything comes from. It is definitely not 100% completed and there is little hope it ever will be 100%.
It is still scientific meaning it can be reproduced and the results will always be the same.
No other view or theory about our background is as complete as a scientific one.
Religion is no theory at all and just a opinion based on 0 knowledge, facts or measurable results.
the big bang isnt a theory of where everything comes from. there is zero hope it will ever be such a thing. by defintion science is incapable of providing any information on the subject.
the big bang trasces the history of the universe back to a dense and hot state. what was before that, what caused that state of being? it is silent. what caused the fast expansion known as th ebig bang? it is silent. why do "quantum fluctuations" occur? it is silent.
what caused it to happen? where did it come from? <--- two questions that always apply to any scientific finding/theory... ad infinitum