The book's very well-constructed that way, actually—make assertions that the thinking reader will have objections to or questions about, proceed to directly call out and address same in following paragraphs—but apparently some people's eyes go so red on reading something they don't immediately agree with that they totally miss the explanation and defense that follows. In short, many of them accuse the book of specific sins it did not commit. Others don't provide enough specific criticism to be analyzable, usually accusing it of the same sorts of problems but without enough details to tell whether the reviewer's just a bad reader like a lot of the other people dumping on it.
Possibly there are good negative reviews out there, but a good percentage of them seem to be folks who are, bluntly, not literate enough to read the book—though it's far from a challenging read.
All history is viewed through the eyes of the author's politics. I accept that, and set my personal politics aside and considered his history. One of the major positives of this book is its ambitious scope. The narrative spans millenia of history and I respect that ambition.
I don't agree with everything Graeber says but he proposes new ideas (to me at least). Those new ideas are fun to consider and think about.