I've recently come across this argument: "IQ is measuring abstract intelligence, not intelligence as a general concept, hence is proved by my source" (non-source quote).
The source was this: https://som.yale.edu/news/2009/11/why-high-iq-doesnt-mean-youre-smart
In this OP, I am going to defend the validity of I.Q. and how it relates to measuring intelligence.
Now, in the article's words, they believe recording a high I.Q. doesn't make you smart because:
"...the [I.Q.] tests fall down when it comes to measuring those abilities crucial to making good judgements in real-life situations. That's because they are unable to assess things such as a person's ability to critically weigh up information, or whether an individual can override the intuitive cognitive biases that can lead us astray."
This "making good judgements in real-life situations" is what the non-source quote is referring to as "intelligence as a general concept". "Making good judgements in real-life situations" is something that isn't necessarily wholly based on intelligence, as sometimes you do not have all information regarding a situation. Absence of all knowledge can sometimes force a bad judgement, despite making a good judgement with the information you had.
Furthermore, other factors such as life-experience will inappropriately weight this metric in favour of older people, as sometimes they will be handle "real-life situations" based on their experience of the past, of which might have been negative and hence they learned from it.
Furthermore still, sometimes people will inadvertently handle a real-life situation well through sheer luck, rather than intelligent thought.
Thus, due to these confounding variables, "making good judgements in real-life situations" has components that you precisely DO NOT want in a measurement of intelligence, because it dilutes measurement of intelligence with facets that are not measuring intelligence.
Interestingly, I.Q. is actually an excellent predictor of positive life outcomes (which extend from "making good judgements in real-life situations"). On page 65 of "The Scientific American Book of The Brain," we see that I.Q. is a predictor of positive life outcomes https://i.imgur.com/WwSHDHN.png . According to a longitudinal study, education level, occupation level and income level were all best predicted by I.Q. https://emilkirkegaard.dk/en/wp-content/uploads/Intelligence-and-socioeconomic-success-A-meta-analytic-review-of-longitudinal-research.pdf . So, there is strong correlation with I.Q. and "making good judgements in real-life situations" anyway.
Whilst it is true to say a person with high I.Q. won't always make "good judgments in real-life situations", it is also true to say that a person with a high I.Q. is more intelligent than a person with a low I.Q.