>>7488278>A high IQ is not a predictor of successBut it is though. You fundamentally misunderstand the measurement as a whole. You are right that it is better at differentiating extrema than anything, but that doesn't mean IQ isn't correlated with success and nothing you have said supports this claim.
Just because the relationship is non-linear doesn't mean that the relationship doesn't exist. Even if the correlation does not increase linearly with IQ, say after a cutoff point of 130-140, that doesn't mean that there isn't still a correlation to speak of.
For example, we can use the data to determine that someone with an IQ of 130 is much more likely to attain some level of higher education than someone at 70. But that fact that this correlation stops increasing linearly past 130 doesn't mean that the person with an IQ of 165 isn't any more likely to get a degree than the 70 guy. Because they are.
