100% write him off, at least any time he diverges into his alt-history.

People like Hancock rely on people not knowing anything and trusting that he must know what he's talking about because look at how confidently he says stuff. But anyone who actually studies history, archaeology, and is even vaguely familiar with the evidence he uses can see right through it. He knows this, and that's why he targets amateurs and why he pretends there's some grand conspiracy against him from academia, that way when people call him out he can go "see, I told you, the academics are just out to get me!" it's very convenient for him.

https://theconversation.com/with-netflixs-ancient-apocalypse-graham-hancock-has-declared-war-on-archaeologists-194881

This bit in particular highlights the problems with him well

>From my perspective as an archaeologist, the show is surprisingly (or perhaps unsurprisingly) lacking in evidence to support Hancock’s theory of an advanced, global ice age civilisation. The only site Hancock visits that actually dates to near the end of the ice age is Göbekli Tepe in modern Turkey.

>Instead, Hancock visits several North American mound sites, pyramids in Mexico, and sites stretching from Malta to Indonesia, which Hancock is convinced all help prove his theory. However, all of these sites have been published on in detail by archaeologists, and a plethora of evidence indicates they date thousands of years after the ice age.

Most people won't know when those sites date to, academics studying them do, but most people listening to Netflix won't, so when Graham uses them all to try and prove his point only those educated will go "hey, wait a second, that dating doesn't even match up with what you're arguing"

Upon which Hancock just pulls out the trustworthy "archaeologists don't know what they're talking about, but you can trust ME" Nothing you can really do about those types of people, they refuse to actually engage in debate or prove their points.