For a long time, the common wisdom is that megafauna died out soon after humans arrived in the Americas. If humans have been in the Americas for much longer than thought, and co-existed with megafauna for millennia, then that narrative is wrong. It’s a projection of modern humans’ faults onto ancient humans. Moreover, it shows that there is nothing inevitable about human-caused extinctions. Humans are not a virus, Agent Smith.
I agree we need an explanation, however we can at this point discard the Clovis-first theory. Too much evidence has accumulated that people have been in the Americas for longer. Whether they died out or are the ancestors of Indigenous Americans is unknown. Perhaps we can discard the hypothesis that humans inevitably caused the megafauna extinctions. Your theory is plausible that it could have been a later technological or cultural change that led to the extinctions. But at this point we just need to accumulate evidence without any strict theory. Any new discovery could sink a theory, with such scant evidence of pre-Clovis ways of life. We know people were there but have little idea of how they lived.
The writing has been on the wall for Clovis-first for decades now, so I’m glad mainstream anthropology is starting to come around on this.
But I still fundamentally think that the timing and nature of megafauna extinctions across the world is difficult or impossible to explain without human hunting as a major factor. Other mass extinctions were not so exclusively confined to large animals, and there is no other competing explanation for this aspect that I have heard.
But of course, we should follow where the evidence leads. It’s just that the passage of time has destroyed most of it, unfortunately.