I think IQ is more potent than most people suspect, because pattern recognition and manipulation is an (or even the) extremely fundamental aspect of intelligence.

Studies do bear out the notion that it's an objective measure of something, because people do well in disparate fields; language, logic, art: if you score highly in one you'll tend to score highly in another. This is called the 'g-factor'.

Studies also show that such traits are extremely heritable.

The only objections I've ever heard are on the basis of some kind of 'higher liberal values', not actual analysis of reality.