Have you read any of his other stuff? His essay on Bullshit Jobs (
https://strikemag.org/bullshit-jobs/) is a good example that isn't book-length (though he did write a book of the same name that came out later)
Here I definitely take his condescending / snarky tone with a grain of salt, but as a reader I understand it as largely a literary technique to build a narrative and suggest / propose an alternative, usually somewhat contrarian, viewpoint.
I can't at all disagree with you here re: Dawn of Everything, as I haven't read the book, but is it at all possible that -- given we're analyzing the reported history of indigenous societies and the book talks about a proposed alternative viewpoint -- some level of "matter of fact"-ness works in a similar way as a literary technique? In this context it seems impossible to truly make a definitive claim one way or the other, as we're talking about histories for groups of people (who were largely extinguished by invading colonialist armies; Guns Germs and Steel and all that...) that are no longer around in serious enough numbers to have an oral history, let alone a quasi-accurate one.
https://en.wikipedia.org/wiki/The_Dawn_of_Everything#Recepti... seems largely like reception was a mixed bag, and that while there are parts that are a bit of a stretch, most anthropologists and reviewers found it a refreshing read contrary to the "canonical" (imperialist) narrative(s) commonly taught in history class. Is it as "mixed" from your read as that Wikipedia summary says, or do you find the discrepancies/inaccuracies significantly more egregious than the way I'm characterizing them?