Much of our culture applauds the anti-consensus actor, the lone visionary who goes ahead despite the disapproval of the crowd. And that's understandable. As Spike Milligan put it "Progress is like an old car. It takes a crank to get things started." Progress depends upon the unreasonable man. What looks like "knowledge over-confidence" turns out to be "justified confidence" in widely unrecognised truths. Further, in entrepreneurial circles, if you're prepared to risk your own money and time on a crazed venture then that's celebrated.
But in reality you create risks to externalities far beyond your own wallet. Such a culture absolves the reckless engineer of causing great harms because they are "a genius" and we want to ride their coat tails. Some of this seeped into Silicon Valley culture where many tech people see the digital world as their own personal laboratory to experiment on masses like bugs in a petri dish.
This could be contrasted with the socially conscious non-consensus actor, who departs from crowd wisdom at great personal loss and just wants to be left alone to do their own thing. That's a different breed of individualism. It's often rooted in falliblism rather than over-confidence. Such a person, out of wisdom, knows how stupid they can be themself, and sees the crowd as no better.
I would say dangers at the other end of the spectrum, of blind unthinking assent, group-think, conflict avoidance, is much better documented and understood. Whether that's a negative or positive depends on the context. On a frontier rugged individualism is an asset while more measured conformity tends to work in long established communities. The contrast of the North American frontiersman and the Nordic observer of small town "Jante Law" is marked.
it's a literal luxury to have enough time and mental space to think for more than a few minutes on any given issue. that's one of the most valuable "legs up" that wealth gives you, not so much the money itself, but the room to think (and unfortunately, often to try to manipulate the world around you in a self-serving/self-centered way--the corrupting of personal integrity that's as old as time).
note that these aren't mutually exclusive groups of people, but typically phases of our own selves. for example, i rarely want chain food, but every once in a while i do. and sometimes i go and enjoy it because the people i'm with want it and enjoy it.
Yet I observe people reaching for their phone-distractor device when confronted with a moment of free time.
In a society where those in power are are not only primarily motivated to achieve a healthier society and nation, but also have the intelligence and wisdom to achieve it - then following the mainstream consensus could achieve something quite remarkable.
In a society where those in power are primarily motivated by their own interests, or lack the wisdom or intelligence to positively lead society forward, then of course everybody following the mainstream consensus means you're, vice versa, headed towards something quite awful.
Specifically, it says that the people “following mainstream consensus” are actually less likely to do so “blindly”, i. e. overconfidently.
So the answer would seem to be: rather low.
After the past few years, I’m really not sure if there is anyone left that doesn’t have a personal anecdote against this.