Thank goodness never did TOS did "doom and gloom," aside from, okay, the Talosians torturing Pike in the first pilot, Kirk having to kill his best friend in the second pilot, and McCoy discovering that his lost love has been killed and replaced by a Salt Vampire in the first-aired episode . . ..
How dare DISCOVERY begin with bad things happening!
(I swear to God, if "City on the Edge of Forever" debuted today, half the internet would be complaining "Where's the hope? Where's the optimism? The REAL Kirk would never let an innocent woman die!")