All it proves was that the dilemma itself is effective.
The episode and its resolution are crap, because they don't justify her decision. They leave it to the viewer. They do a disservice to everyone involved.
Tuvix wasn't some alien body snatcher who possessed the bodies of the deceased. He was literally Tuvok and Neelix living on in a new form, which comprised a third entity.
In killing Tuvix, Janeway also murdered both Neelix and Tuvok.
What she did, in essence, was to murder three people to bring back two.
There being a method of resurrection doesn't make a person any less dead. They were dead, but Janeway the necromancer knew how to bring them back to life. All it took was a sacrifice.
"we look for rings"