You've heard nonsense. Please read some of the literature on intelligence research (1). Steven Pinker has also written a great book on why the ideas of the blank slate and social constructivism are purely ideological and do not hold up to analysis (2).

IQ is a very strong metric predictor of pretty much every aspect of personal success, from successful marriages to income to academic achievement to interpersonal skills. By no means is the relationship deterministic, but that isn't what we mean by predictors. (Many other psychological metrics, like the nonsensical "emotional intelligence", predict nothing when IQ is included in the mix.)

1: https://www.amazon.com/Neuroscience-Intelligence-Cambridge-F...

2: https://www.amazon.com/Blank-Slate-Modern-Denial-Nature/dp/0...