IQ might be a better predictor, but the linked paper says it's not a far better one:
"The results demonstrate that intelligence is a powerful predictor of success but, on the whole, not an overwhelmingly better predictor than parental SES or grades."
That might just mean that intelligence is useful not only for gaining personal success, but also for raising offspring who will be successful. Is that a problem that society should try to correct?
"The results demonstrate that intelligence is a powerful predictor of success but, on the whole, not an overwhelmingly better predictor than parental SES or grades."