For most of human history people lived under the social systems these people are advocating. Enlightenment civilization, of which democracy and free markets are only two components, is less than 400 years old, and in that time we've seen a flowering of technological and cultural growth that dwarfs everything else that happened in the previous millennia of human civilization. Coincidence? Perhaps. But I think it more likely the neo-reactionaries are analogous to the cranks who write papers claiming to disprove quantum physics and then post them to the world using tools which depend upon those physics to function.
Science fiction author and Enlightenment champion David Brin has a blog post exploring some disadvantages of neo-feudalism. In that article he links to the Anti-reactionary FAQ with detailed criticisms of their arguments and goals.