Yeah, I get it in the TV Show Kirk & Company/Picard & Company all beamed down, cuz no one wants to watch an away team of people you never met before (well, in Lower Decks could be a exception to the rule).
But in the books, there is a little more latitude, yeah...a lot of readers want Kirk & Company, but don't force some character to have scenes when it just a plot device.
Chris, I get your point how you created Chen, but maybe having her start out as Contact Specialist limited her to begin with since the crew wasn't really interacting with Strange New Worlds...
For example, I'd say the same thing if Chen started out as Stellar Cartography, if in the first book they were really mapping stars, so don't make her a medical tech in the next book cuz mapping stars is not part of the plot, and then running engineering when Geordi and the other engineering crew are down on the planet cuz nothing in the book calls for scenes in sickbay......if she's gonna be mentored by Picard, dat one thing, but don't cram it down our throats.
You cite Chapel as an example...but lots of episodes went by for Chapel to grow + it makes more reasonable sense for Chapel to be nurse to Doctor....unlike Contact Specialist to Adjudant to Officer of the Deck. I'd have a bone to pick with Chapel if all of sudden Chapel became a helmsman then a security officer.
Lastly, you say, "The bottom line is that, again, this is fiction rather than reality, and characters get moved to new jobs based on what works for the story. "
Agreed, the use of Chen is more plot device than anything else and so people don't want to buy into her character (except for being the annoying pre-teen younger sister!)