I think speed limits help people not die

I do too, except the way they have evolved is terrible.

They're (almost all) the same day, night, rain, shine, sleet, snow or ice.

They're primarily enforced on nice sunny days when it's not uncomfortable for the officers to be standing outside their cars.

They're almost never enforced on the busiest roads during rush hours.

Within the US road funding system, the busiest roads get their speed limits raised in order to increase their "Level of Service" to prevent them from losing federal funding. US1 south out of downtowm Miami is a damn nighmare at 45mph with all the traffic it carries, but other similarly configured roads which are straighter with better sightlines fewer side streets and less traffic get 35mph speed limits because they won't lose their funding for low LOS issues. (my info may be out of date about US1, I left Miami 25 years ago, but while I was working at DOT classifying roads in the 1990s I had to commute that death trap.)

And then you can start talking about the small towns that use speed enforcement as a source of revenue.