If it isn't measuring intelligence, what exactly is it measuring?
They are measuring a very narrow part of intelligence. Spatial. But there's a whole lot more to intelligence than that and it can't be compressed into a single score. That is ridiculous. Besides, you can get better at it: just keep solving the kind of puzzles basic IQ test gives you and you'll get better. Which doesn't mean you have become a more intelligent.
"The fact that an opinion has been widely held is no evidence whatever that it is not utterly absurd."
- Bernard Russell
"Only two things are infinite. The universe, and human stupidity, but I'm not sure about the former." -Albert Einstein "You know you're in love when you can't fall asleep because reality is finally better than your dreams." -Dr. Seuss "If you want to know what a man is like, take a good look at how he treats his inferiors, not his equals." -J. K. Rowling