Fatalities have gone down even for wars of similar intensities. More important is the improvement in battlefield medicine and body armor - the KIA/WIA ratio for the US military has plummeted, from around 1:1.5 during WW2, to around 1:3 in Korea after the introduction of helicopter evacuation and more refined frontline aid stations, to just above 1:10 in Afghanistan.

e.g. I strongly doubt that Tammy Duckworth's wounds would have been survivable on the battlefield in 1940, or even in 1970.