Listen to that well-dressed Porg up there, he’s talking sense. Discovery is designed to be one long arc which is a different to most* of the other series story structures. It stands to reason that the characters will develop as things progress doesn’t it? If everyone was fully formed by the end of the pilot and the rest of the series was them just getting into adventures it would be a bit dull (and Voyager kind of already took that approach.)

*yes, I know what Enterprise did in its third season.