You said that for captain to be non-male, their name would need to be "Captaina", which implies that captains cannot be women, because they'd need to be called "Captainas", which makes zero sense at all, and legitimately belongs in a kids show.
Well, then I didn't misunderstand you. You're saying that in order for Captain to be not male, they'd need to be named "Captaina". Which implies that women (and other non-male individuals) cannot be referred to as "captain" because according to you, that's "masculine".
If anything, I'm apparently misunderstood, because I never labelled you as a sexist, I just questioned your less-than-logical logic.