They try to end the article with some feel-good hand-waiving, but so many things have changed since the mid 1970s, that it feels ridiculous to use lack of formal reasoning as an excuse. Since there's no data on it, nor on "fluid intelligence", there's no reason to assume later generations have more or less of either. If they do lack "crystallized intelligence", they did indeed become dumber.
They try to end the article with some feel-good hand-waiving, but so many things have changed since the mid 1970s, that it feels ridiculous to use lack of formal reasoning as an excuse. Since there's no data on it, nor on "fluid intelligence", there's no reason to assume later generations have more or less of either. If they do lack "crystallized intelligence", they did indeed become dumber.