It’s a classic, if somewhat exaggerated trope in Star Trek: The ships first officer, second officer, tactical officer, chief engineer, chief medical officer, and a random ensign beam down to an unsecured planet while some dangerous problem is either ongoing or likely to occur. The Doylist reasons for this are as obvious as the Watsonian reasons it seems so silly: these are the main characters who are supposed to get the bulk of the screen time, so they are constantly thrown into situations which real world commanding officers and department heads are generally kept well clear of.
But what if this wasn’t the precedent established in TOS and continued in every subsequent series (including, to a slightly lesser but very real extent, Lower Decks)? What would a Star Trek show look like which still had senior officers who we are meant to care about and who still get significant development and screen time, but who aren’t thrown into unrealistically dangerous situations on a regular basis? Could such a show survive telling stories without visibly putting those regulars lives on the line so frequently? Would it be viable to keep the focus on things that happen either aboard ship or in nominally safe situations? Alternately, could a show successfully develop a cast of lower ranking “away team” characters who get the “dangerous” screen time while keeping significant focus on the major decision makers on the bridge? And how could the shows manage such a visible separation between “expendable” and “not expendable” crew while maintaining that humanist, optimistic, everybody-has-an-equal-right-to-life ethos?
It wouldn’t be an easy thing to pull off, certainly. But how could it have been done?
I think this can quite easily be pulled off. Lower Decks is an example of this to a degree, but for an even better Beta Canon example look at the Star Trek Resurgence narrative game. The story takes place from two perspectives Petty Officer and the ship’s First Officer. Each of these characters has relationships which will impact the story and for the most part they work separately from one another, but still work together and it makes a lot more sense when the Captain sends the Petty Officers to go on the hull and do dangerous work than sending the chief of any department.
Consider that Deep Space 9’s primary cast of characters includes an enlisted person and several non-Starfleet personnel or straight up civilians. Porting that to a TV show would not be that difficult and I think there has even been some success with that in Lower Decks which features lower deckers along senior staff just fine, even interweaving their stories; and Discovery which, particularly in the first season, creates characters by proximity to the story not by bridge positions. Tilly is important because she is Burnham’s roommate, not because she’s the chief of anything. Despite this Tilly’s character is a fan favorite. Unfortunately, I think Discovery fell into the impulse of giving audiences more of what they want and that meant creating stories where a random cadet was a valued member of the team - and team was still mostly senior staff.
That’s actually an excellent point with early Discovery, a connection which had not occured to me despite working on this morning’s post. Discovery absolutely does try to do this, and for the most part it works; it only really falls apart when the show shifts to extremely grandiose storylines and feels the need to put Burnham in the middle of all of them. The early goings, essentially a war story told from the perspective of some science specialists who really ought to be the ones in the middle of those situations, makes considerable sense.
That post is actually what made me consider how well Discovery managed to do what the OP mentions in their first season. Answering the question of “why send all the senior staff” by making the main players not senior staff just works.