In essence the white heterosexual young male lead the hero of a 1960's American prime time network television show... FAILS.
To me that's pretty fucking brave at a time when the expectation was that the "hero" would always have all the answers regardless of the circumstances.
I think your premise about mainstream American television of the 60's is a cliché and I don't see any connection with bravery (or cowardice). Charlie and the Thasians had superpowers...and those superpowers itself had limitations. In fact, the Thasians failed too.
Kirk and his crew will have their ass saved by powerful alien being on other occasions too, it's a part of the deal when you decide to explore space. Errand of Mercy is a paradox: it's a failure, because they're owned by the Organians, and a success, because a war is avoided. In "Who Mourns for Adonais?" they will have a bitter victory against an ancient god.
Oh, and thanks Nebusj for your observation.