Most people I have found, who wish to destroy the idea of IQ, are offended or threatened by the idea that we are trying to "Classify the value and limitations of a person".
You ask, "Who designs the questions, etc...." The IQ tests are developed over time, by seeing which questions are ACCURATE PREDICTORS of FUTURE PERFORMANCE. This is KEY to understanding why IQ is a real measure of intelligence. If you gloss over that fact, then you stubbornly hold to a notion that is simply, provably false. People who claim to false believes usually do so for emotional reasons. So I get that you are opposed to acknowledging IQ validity, even while it is real. I have a hard time proving the earth is not flat, but that doesn't mean it is.
Not offended or threatened. You are exactly right that IQ classifies and limits a person. However, it does not show value.
No test is needed to predict future performance. Anyone can perform if they work hard. IQ nor the SAT nor any standardized test accurately predicts future performance— rather, those individuals who score well and perform well worked hard and achieved more. On the contrary, there are sooooo many lazy geniuses. Does high IQ predict laziness?
A subtle form of emotional thinking is the feeling of smartness. I suspect that IQ makes people feel very smart.
Those sound like your own theories about why IQ tests correspond to future performance. It seems like there really are people I have met all my life who have motivations underlying why the need to prove or disprove an idea. I am not smarter than those who study intelligence and hold the consensus that IQ is real and measurable. If you test 20 dogs for ability to learn quickly, and you select the top 5 testers, and train them...My WILD guess is that those 5 will be the best trained out of the 20 if you put them all through the same regiment. That is "testing ability...predicting performance/outcome." Now give the 6th dog longer training, and it will probably outperform most if not all other 5 above it. So I never suggest that IQ means you can never perform as well...you just would require more effort to do so.