It can't be scientific and objective, because it is not measuring something scientifically and objectively defined and most of the differences being discussed can be erased by manipulating the testing circumstances.
That doesn't mean it is never worth measuring, but it seems particularly silly to obsess over IQ when better data on actual outcomes exists for things like educational interventions. The best applications of IQ are in identifying areas of deficit in individuals (one definition of learning disability is an area of cognitive performance that varies significantly from all others.) The worst applications of IQ are to funnel more resources to already-advantaged children or to make demographic generalizations. Given that, it hardly seems unreasonable to mostly ignore the IQ-obsessed research and focus on specific, repeatably-defined cognitive tasks instead.
That doesn't mean it is never worth measuring, but it seems particularly silly to obsess over IQ when better data on actual outcomes exists for things like educational interventions. The best applications of IQ are in identifying areas of deficit in individuals (one definition of learning disability is an area of cognitive performance that varies significantly from all others.) The worst applications of IQ are to funnel more resources to already-advantaged children or to make demographic generalizations. Given that, it hardly seems unreasonable to mostly ignore the IQ-obsessed research and focus on specific, repeatably-defined cognitive tasks instead.