There's been 1000's of studies on it. It might be one of the most robust findings in all of psychology and psychometrics (Big 5 is in the same ballpark). You can predict all sorts of things from it. If IQ is a bad measurement, than there are no good measurements in psychology.
If coding is done by AI that will mean humans will be hired to do something else and whatever that something else is, the interview process will try to measure how good a candidate is at doing that thing the candidate is being hired for, whatever that thing is
Imagine it like this, if we give someone a history test, a math test, a physics test, and english test. We'll notice how good you are at any given tests predicts how good you are at other tests. Even though math and history don't have any real overlap in terms of skills. They also found that doing well on some of these tests will better predict how well you'll do at others. For instance math and physics are typically more g-loaded so if someone does well on a math or physics test they are more likely to do well on an english test than the reverse. We call this quality of that predicts how well you're going to do at intellectual tasks g. And then we built a test to try to measure G and that's an IQ test, with IQ being the measurement of g.
People say stuff like this all the time as if it's an uncontroversial fact, and it's much less supported by the literature than you're implying. So much of this is a matter of interpretation and the people interpreting it are generally people personally vested in the concept of IQ
https://pmc.ncbi.nlm.nih.gov/articles/PMC4557354/
I do agree that an IQ test can help measure severe intellectual impairment, or a change in an individual's ability because of illness or injury. I have a lot of doubts about it's meaningfulness beyond that.
Almost all of which can also be predicted pretty well using your zip code. Are you sure IQ is measuring something internal?