The show has had Mariner state several times that she believes being an ensign is where the real action is, that ranking officers are unnecessarily obsessed with seeking glory and a place in the history books, that Starfleet has too much red tape. There's the implcation that she has issues with her captain mommy and admiral daddy. The whole subplot with her being promoted to lieutenant was about having to do a bunch of BS as a ranking officer she found tedious, which is saying something since she could derive joy from even the crappiest of ensign jobs. Basically, what she likes out of Starfleet (space exploration, mysteries, saving people, cool friends) she can get out of her current position, being a ranking officer doesn't really get her more of those things and comes with a bunch of stuff she doesn't want or like (obnoxious glory-seekers, following every stupid protocol to the letter).
I don't know what the Boimler line had to do with "Gen-X-type cynical crap," as I'm sure that sort of notion could be found in comedy dating way before Gen-X was a twinkle in their parents' eyes. Nor do I understand where the betrayal of a friendship comes in.
With three of the five main human characters being people of color, why does it matter that their names happen to be Anglo sounding? Would it make a difference, really, if Sam Rutherford were Sam Ramirez or Beckett Mariner were Bahati M'benga?