This is what usually prevents me from understanding longtermist arguments. I'm not convinced think the average person from even ~100 years ago would be able to

This is what usually prevents me from understanding longtermist arguments. I'm not convinced think the average person from even ~100 years ago would be able to do anything about (what I would consider) most of the biggest problems of today, and besides structural changes (governance, suffrage, etc.) I don't know what they could realistically have foreseen as the correct thing to do to solve problems >= 100yrs out. Why would I presume to know the problems of >= 100 yrs from now? It seems like the obvious path is addressing structural issues, supporting effective research, and beating out various fires (all of which are pretty much neartermist concerns). To abuse a thought experiment, I care about the child running through the woods 100 years from now as much as the child today, but I would place way, way higher likelihood of broken glass on the ground hurting the child today.