The increase is mostly attributable to 30-39 year olds on arterial highways at night.

Kids playing on neighborhood streets show continued improvement... In fact IIHS pedestrian fatality data says that 1-13 year olds are the group with the HIGHEST reduction

That data shows a local minimum in 2009 and suggests that pedestrian deaths were higher during the "golden age" the commenter is referring to than today, and that is in spite of many more cars on the road today

Another gem from your own source that refutes this entire line of reasoning:

"Deaths of children under 10 are actually down significantly (167 deaths in 2009 to 98 deaths in 2023), and deaths for ages 10-19 are down as well."