IQ is highly predictive of the outcomes of future IQ tests, and to a degree academic performance (though much of academic measurement is based on similar theories, so this is unsurprising)

There's much less corellation when you consider "future success" in terms of things like job performance, financial success, happiness, et cetera. IQ is obviously measuring something, because IQ tests are quite reliable, but the thing it's measuring does not seem to show a strong corellation with a lot of real-world goals.

It's one of those measurements that people _want_ to use a lot, and so it sees a lot of use, but the idea that you can boil general intelligence down to one number is fallacious to begin with, so many of the things it's used for are not useful.

This is literally one of the things the post we're commenting on is saying. High IQ people are not automatically successful and whatever effect high IQ may or may not have on future success is easily lost in other, more significant, factors.