I think you're being uncharitable towards the critiques. In particular Hanson doesn't actually address the manipulation most of these critiques are talking about. See e.g. https://news.ycombinator.com/item?id=28541243
Moreover even among futarchy proponents, many do not advocate for it as the dominant form of government, but only one form for certain operations. Hanson's position is on the more extreme edge here.
Do a search for "manipulate" in the text for a simple counter-argument.
tellingly. None of the critiques I see address these counterarguments even, so I suspect knee-jerk responses are mostly whats posted here.