[c_i_v]

Willful ignorance has always been an option, and there is no reason to believe there has been significant change in the last millennia with respect to individuals.

Willful ignorance implies knowledge that is available, but disregarded since it isn't desired; and, the knowledge someone holds is not dependent on its validity.

What has changed is the availability of different ways of thinking and the increased number of ways they go unchallenged in public discourse. With the addition of the internet/mass communication, the memes that self reinforce the strongest allow their carriers "know" with more "evidence backed" certainty than ever (albeit with more competing ways to doubt them too).