Theres nothing startling about it. These are the type of people who will never have kids but will do anything to influence yours, will swear they want to teach them to read while taking away phonics, will sell your country's jobs overseas and swear it secures prosperity and call themselves harbingers of truth but only ever lie. Such utopians as these are a scourge and they will do whatever they can to take your sex, take your vices, take away your ability to love and keep secrets. The last man can only be brought forth as a spirit from them and if they had their way humanity would be nothing but the most soulless of cogs.The only problem is that democracy isn't about "governing yourself," but rather, governing other people (e.g. your neighbors, future neighbors, society as a whole, etc). No system of government is about "self-government" (other than anarchism). It's about managing the social contract between different people/groups.
What the body of research he is citing really boils down to is that people are tribal, irrational, and bad at governing each other in a mutually beneficial way. Elites tend to be bad at it too, but Rosenberg seems to dismiss that concern. The presupposition that almost always goes unchallenged in these arguments is that a high level of governance and social organization is beneficial or necessary. If large underlying social forces like the Internet or social media are corrupting government with "evil populism" and making it impossible for democracies to govern well, then why not simply govern less? "Bad leaders" in government aren't really that scary when they don't have much power.
The substance behind the paper is not really new or shocking, the startling part is the (((conclusions))) about ideal methods of governance (i.e. oligarchy) that the author reaches based on his evidence.