I don’t think this is an argument against the usefulness of IQ. Firstly not all countries use standardized tests with such an influence (I’m from Czechia and we don’t, there’s a standardized high school leaving examination, but it’s only necessary to pass, the score is generally unimportant for university admission). Secondly all you’re saying is that the tests correlate with IQ. That does not make them or IQ invalid, it may just as well simply mean that they test how well a student does in school, and having a higher IQ tends to make studying easier.

But mostly, again, psychometrics is the one field of psychology that has relatively rigorous and reliable methodology. The idea that you disprove decades of research, from large scale statistic studies made with cooperation of state institutions to expensive and rare research like various twin studies, simply by saying “actually IQ doesn’t matter” is naive at best. There really isn’t a lot of reasons to say that apart from ideological ones.