Nobody debunks him really, tho, because he speculates about things we really know very little about. Nobody has Facts about early human civilisation. it's like getting all frothy and posting angry debunking videos about how alien life might exist in the universe, it's funny that that doesn't happen.
I think he's wrong and takes giant leaps to his conclusions from the little evidence we have, but that's the problem we have very little evidence to claim anything as fact.
I think people get hung up on him banging on about "advanced civilisations" like it must mean there was some pew pew laser flying car drug smoking people 50,000 years ago.
Modern humans have been around 200,000 to 75,000 years, maybe longer depending on definitions, we can't even really decide on that I don't see the harm is speculating why nothing seemed to happen technologically for 95% of that time.
A real debunk would be to prove and explain what changed in humans 5,000 years odd ago to allow for a rapid acceleration in technology and understanding, be careful tho nearly everyone that has done that ends up doing a racism