Yes, the myths definitely need busting. To explain what I mean a little more: No doubt there were differences between Neanderthals, Denisovans, and 'Sapiens' (and I've never understood why differences in brain case size are considered significant), but what I'm mainly concerned with here are definitions, i.e. how much difference is possible within a 'species'.
(NB I also don't like using the word 'interbreed' when speaking about people, although when I first started to think about this, I used it myself.)
Now, I realise this may not be current thinking any more, but I always thought that 'species' was defined as 'can produce fertile offspring with one another', between male and female in the case of mammals, for instance. All I've ever read suggests to me very strongly that all human groups were able to produce fertile offspring together, and that they are all woven into our story. I seriously doubt that any group of humans ever fully 'died out' or 'became extinct'. Sure, they bashed each others' heads in all the time, like humans have always done, but they also produced fertile offspring.
My question has long been how much difference remains after that to still call different humans members of different 'species'. What does 'species' mean if it's not special enough to procreate alone? I strongly suspect that it's simply inapplicable to humans. I think that if we were to find any evidence of different human species, it would be in the very early stages of our evolution, i.e. probably in Africa, but probably not outside it. Obviously, we have various extremely old fossils from across a long, long period of time, and it's possible that those at the start of the development would not have been able to produce fertile offspring with those at or towards the end of the chain, because by then significant enough changes in their composition had taken hold, but I think it most likely that people would always have been part of one contemporaneous species.
Again, I'm no expert, just an armchair conjecturist, and one reason why I care about the answer to this is because I think establishing beyond doubt that there have never been any really significant differences between people would help to some extent with the fight against racism.