All the examples so far posted here of the reasons why post-industrialized humans are less intelligent or resourceful than pre-industrialized/industrialized persons are based on personal value judgements. In other words, you believe cooking your own food is important, for example.
But, in areas of the world where there are restaurants on every corner- cooking is a choice, not a necessity.
In undeveloped areas of the world where grains/fruits still needs to be grown, meat products tended to and prepared in order to eat- cooking is a necessity and a means to survive.
The intelligence is in the human consuming food to match the demands of their environment.
In our own society, we have agricultural, rural areas that are on the borders of urban spaces- here people can both grow and prepare their foods (cook) or take a ride into town and grab some prepackaged foods at the grocery store or prepared food at a restaurant.
In an urban space it is possible to stay healthy, if good choices are made, by not cooking a meal.
Again, to say a person is not as intelligent in modern times because they cannot cook ( and there are many other value judgements made here along these same lines) is something you believe is important. For some it is- for others it is not.