IQ testing is reification fallacy. If I told you I had an instrument that could objectively measure every human by how beautiful they are, you'd see the problem immediately.

IQ depends on their being one kind of intelligence. You only get one score and it's the supposed measure of general intelligence. If street smarts vs. book smarts is a thing, IQ cannot be.

IQ measures racial difference that cannot be biological. Race is cultural, so since the test measures consistent difference between racial lines, it's proof that it's not measuring something biologically determined. It'd be like if IQ showed blondes really were dimmer than their peers, but you found out the effect carried over to bottle blondes.

I recommend the book "Mismeasure of Man" by Gould. His thesis shows the historical folly and logical impossibility of not just IQ, but biological determinism. I've just posted the common sense arguments against IQ, Gould brings the receipts.

Not only that, but a lot of developmental disabilities are only recognized as needing accommodations if the person scores low enough on an IQ test. But many score high on these tests, but do poorly in school because they are stuck in a system that only values people who learn from lecture, repetition, and regurgitation. So they are considered lazy rather than needing help.

My favorite argument agents IQ is that every thing it claims "inherent quality", "can't be studied for" ect were exactly what the SAT used to claim.