I didn't say they didn't have clothing. But there is nothing to show innovativeness in terms of clothing.
You can't claim Neanderthal had the rapid innovativeness we see in humans in terms of clothing.
No. But I can claim that homosapiens didn't have rapid innovatiness in their clothing during this period either. Which is based on the very basic clothing found on Ötzi in 3500 BC. Is this evidence that humans aren't intelligent? The fact that we later got fancy clothing doesn't mean we suddenly became more intelligent.
I don't think the basic facts have changed.
A very rapid expansion of humans out of Africa to fill the planet which included the extinction of Neanderthal and taking over the places Neanderthal were living. There is also evidence of another species in East Asia that either went extinct on it's own or due to human expansion.
What has changed about this?
The biggest thing is the genetic research. Back then we hadn't even sequenced the entire human DNA. We sure as hell hadn't sequenced the entire neanderthal DNA. Back then we didn't even have the necessary samples to do such a thing. We now have. Not to mention all the genetic studies that have gone on since.
Most critically we have since figured out that the Foxp2 gene is critical for human speech. Monkeys and chimpanzees don't have it. Neanderthals and denisovans do. Exactly in what way the gene is critical is debatable. But the presence of the gene suggests that we can't simply dismiss neanderthal speech.
We've also learned since that humans and neanderthals interbred. Back in 1991 we thought neanderthals and humans were so different they couldn't interbreed. Also humans and denisovans. Diamond didn't know that. We've also found neanderthals with healed broken bones. Evidence that they cared for their sick. Neanderthals likely traded with one another, and with humans. Since then we've also found neanderthal art, and burials. All this is information that Diamond wouldn't have had access to.
We've also learned that a bunch of things attributed to early humans, especially religion is highly dubious speculation. For example, one region we thought they'd placed flowers in graves. Turns out they were placed their by a local rodent. So early humans weren't nearly as advanced as they thought back in 1991. A lot of what we thought we knew about early humans, it turns out we didn't know.
But most importantly, the most complete stone age human we've ever found, Ötzi, was found after the Third Chimpanzee was published. That find radically changed what we'd earlier thought about stone age humans.
The truth is that a hell of a lot has happened since 1991. Especially regarding our view of neanderthals. We don't any longer see them as ataivistic savages. What we're struggling with now is explaining why they died out in spite of their comparative brains with us.
They could have died out because they differed from us mentally. They could have been worse at lying for instance? They could have had instincts propelling them toward a more cooperative and less aggressive behaviour than us. Enter a highly aggressive primate with comparative mental faculties and it'll just be a matter of time. There's just so much we don't know.