The problem I have with IQ tests is many questions are about pattern finding and there is often more than one correct answer.

I'm used to problems being defined more precisely, and when I can think of more than one correct answer, but know only one is correct according to the author, I have to guess which one they had in mind, which I'm not good at.

IQ tests could be designed better, but that would require the use of formalisms, which most people are not familiar with, as everyday life doesn't expose to them.

Also, if you do a lot of IQ tests you can overfit for them and become an expert in solving them, without necessarily being that smart.