A Space Western. It very much was. Watching it in reruns out of sequence, it was difficult to know that Grace Lee Whitney, who played Yoeman Janice Rance, was originally slated as the female lead in the show with a higher rank. She was intended to be like a space exploring Miss Kitty with an understood relationship with Kirk. Shortly in to production, producer Gene Roddenberry ditched her very crudely in favor of his girlfriend, Majel Barrett (Nurse Chapel and the voice of the ship's computer), and his mistress, Nichelle Nichols (Lt. Uhura).
The absence of a true female lead also allowed Roddenberry to abuse his authority with the casting catch. I am no feminist supporter but Roddenberry was a pig, and he hurt the longevity of the show. In retrospect, there should have been more of Grace Whitney on Star Trek. She was beautiful, elegant and classy. She deserved better than what Roddenberry did to her, and how realistic was it that Kirk kept falling in love with aliens with presumably different anatomy than a human female?