for everyday life, i see The Peter Principle everywhere i go (the idea that people get promoted until they reach just above their competence level for that job)

I think these authors may, themselves, be suffering from the Dunning-Kruger effect.

The societal effect of "incompetent people don't know they're incompetent" is likely just as detrimental as "incompetent people know they're incompetent, but think no one else is any better". That is the actual problem. It's where the idiocy of "I do my own research" comes from. The thinking that reading some shit people said on Facebook is just as valid as scientific, peer-reviewed data because "no one knows any better than anyone else" is pretty fuckin' dangerous.

Also, how do they not see that the overwhelming majority of the population thinking they're better than average makes perfect sense and aligns with the original D-K conclusion? If 90% think they're above average, maybe 45% are below and suffer D-K while the other 45% are above, many of whom may be underestimating their skill by only comparing it to the average.

Most illogical atheist will not like it that their Dunning Kruger effect has been debunked. Many illogical atheist like using their Dunning Kruger effect in a condescending way as a part of their sarcasm worship to spaghetti monster when they are making fun of people they think are stupid.

I think that they have perhaps not understood what the Dunning-Kruger effect actually says, since it does state in its original form, that higher level skills, like maths, are an exception anyway. Plus they were dealing with maths students, who you would expect to be in the upper levels of understanding to begin with.