Hmm. And yet, there have been more than a few "what-if" stories regarding Edith Keeler.
Of course, the best tragedies aren't entirely bleak and hopeless (Edith Keeler's demise prevented Hitler from conquering the world; Pike's not acting to prevent the event that would leave him disfigured, disabled, and entirely dependent on the Talosians prevented a disastrous war).
Many would say the best tragedy ever written is Hamlet. Where's the optimism in Hamlet's ending? Umm, Horatio's cool and he survives?
Like Kirk, I don't believe in the no-win scenario.
That doesn't really apply to tragedies, though. A lot of the time, what makes a story tragic is that there was a way to win, but the protagonists' hubris, fatal flaws, or misfortune prevented them from achieving it.