Just a silly theory.
So I read a comment on ROTC, and it was a really good question. It goes like this: If Vast Cold Heavenly Lord was prevalent only 500,000 years ago, and Yang Su Jin only 40,000 years ago, why does the main cast spend several million years advancing to upper immortal or dying? This is in the context of Seh advancing to upper immortal in ten million years, however many years he was in the liberation supreme diety's immortal art, and the seventy million years it took to advance to great net. So I think that the reason we are seeing such slow growth in the main cast is that Hong Fan, or whoever is bringing in enders into the world, is slowly making enders weaker.
First: In the past, there have been enders born with the authority to recreate Mount Sumeru and create their own immortal daos.
Second: Although Vast Cold and Yang Su Jin were prodigies, neither seemed to have had an overwhelming authority, unlike recreating Mount Sumeru.
Thus, using these two data points and how weak the current enders are, I think the audience chamber is granting enders weaker authorities to perhaps experiment. Remember, Kim Young Hoon was the strongest Golden Heavenly King Hyeon Mu ever fought. And why all the current Ender's authorities are so weak.
Important note: I think an authority is different from the power gained after becoming a heavenly king; I might be wrong. As Kim Young Hoon was born with void perception, but his power is grasping truth.