I'd say maybe try to make future medicine more advanced.
How many times does someone die and that's it, no attempt at resuscitation.
Actually, there are episodes where McCoy tried to keep a patient alive, but the person was beyond medical help, such as Kirk's sister-in-law Aurelan ("Operation--Annihilate!") and Joe Tormolen ("The Naked Time").
And I can't understand how some of the characters that died should have, like Miramanee for starters.
Severe internal injuries. She was stoned by her people and by the time the landing party beamed down, she had been left in that condition far too long to be saved.