Even simple things like cryogenically freezing terminal patients until they can be worked on later, are missing from Trek.
It's fun enough that they do address this very thing. That is, in "The Neutral Zone", they run into some patients who were frozen (after their deaths, to be sure, but for the above purpose), and Dr. Crusher brings them back to life as a hobby project, and she and Picard discuss the utter perversity of doing such a thing. It seems that there is some merit in their minds to the idea of freezing a person before
death for later cure, but doing the freezing after
nature has had its way is just plain weird for our heroes. Even if the victim is barely in his forties or whatever.
Certainly none of the TNG era heroes or even of the villains consider prolonging of life a goal worth pursuing. Only a comical sidekick has such aspirations, and even then mainly because the accomplishment would prove his unconventional theories.
Which makes it all the weirder that the same heroes mourn a comrade who died violently in the course of duty (say, "Skin of Evil", "The Ship"). Why is death through violence more objectionable than death through acquired disease or inborn ailment? All involve circumstances conspiring against advanced age.