"Red Shirt" is just a more common reference for "the star doesn't die." If the star dies, you lose your show (or book). Unless you make it a generational tale, like Erik Larsen's Savage Dragon, where there's a character that can fill the lead role when the current lead is dead or retired.

So if you're going to show that the situation is serious and life threatening, you have to take some incidental characters along that you can sacrifice for the story. The idea is to build the illusion that the star could die, without actually killing your star.

The problem with Star Trek is that they never made you feel like the stars were really in danger. They were always going to get out. The Red Shirt became a recognizable pattern as victim, and what that allowed was for the crew to react to the danger, and yell, "Beam us up!"

Next Generation tried to amp up the feel of danger by constantly having something that interfered with their (supposedly more technologically advanced) transporters, so that they were constantly having to set up devices that would boost the strength of the transporter signal.

With Deep Space Nine, the idea of the (mostly) stationary space station somehow clued the writers into something they didn't utilize that much with the ships- the concept of a rotating cast. Yes, we can kill one of the stars, because she's a Trill. We can kill off the host, but transfer the Trill to another host that will gain all of her memories, even though he's a man. We can kill off or demote the Bajoran liaison to the station, because the planet will send us another. And while this strengthened the illusion of danger for the stars, they still weren't going to do any permanent damage to the captain, the doctor, the chief engineer, or Quark and Odo.

I think Voyager did the best job, because they gave themselves the least to work with. They were trapped in a quadrant so far out that it was going to take them seventy-five years to return to Federation space. So whatever humans are aboard now would probably not live to see the Federation again, unless they found something to return them home sooner. There were no Federation allies here, everything was an unknown, and many of them were more powerful and had reinforcements. The core of the crew still remained intact, but I think there was at least one star death along the way (I think). To me, their situation always felt bleak, so everything put them in danger.

"The star doesn't die" is a necessary function of most stories. The hero has to live through whatever happens, because it's what makes them seem more-than-mortal or manly-man or whatever term for hero/heroine you want to label it with. In a one-time story, you don't notice "the star doesn't die" very much, because you can buy into the danger and believe that they could have died. In an ongoing story though, danger gets to be "ho-hum" to the reader, because they know that the hero has to live for the next story.

That's why "deaths don't matter" in comics. The star will always live, and if they don't, they're somebody's favorite, so they'll come back. It's gotten so ridiculous that even incidental characters could return from supposed death, somehow changed and amped to make them a threat.

All of this is why I constantly champion the generational continuity. Make it so Batman can die, or just get too old to carry on, and every story becomes a threat. At some point, Dick Grayson will take over the cowl, Tim might take over from him, Terry McGinnis might take over from him, etc. Superman might be killed by Bizarro, Billy Batson might take over for him, Freddy Freeman might take over for him, etc. Donna Troy might take over for Diana, Cassie might take over for Donna, etc. Just like Bart took over for Wally, who took over for Barry, who (sort of) took over for Jay. Green Lantern probably carries the most believable level of danger, because anyone can be a GL, as long as they are fearless and wearing the ring. So yes, we can kill off the star.

If continuity was truly generational though, then danger would seem real for all of those characters, and we wouldn't have the ridiculous situation where the JLA never ages or dies, but the sidekicks do, even though they can never quite take their mentors' places on the JLA for more than a commercial-hype moment. But then we need more sidekicks, so we bring up another generation in Young Justice, but that's a crud name, so let's make them the new Teen Titans! Which forces our original Titans into literally becoming Outsiders, effectively ruining the marketability of an entire team of characters.

The only unintentional benefit the generational backlog of DC characters has is that as characters are forced into "outsider" status, their popularity wanes, and they eventually drop into "incidental character" status. Which means now we can kill them, and their deaths will be a shock to readers who assumed they would be around forever...even though they will probably return from the dead at a later date, because their death will make them instantly popular again.

Going back to Red Shirts for a minute though, what made them a problem was that their deaths didn't matter. They were completely incidental, even to the stars of the crew. "They died, okay? Just beam us up!" Very rarely was anything done to make you feel the death of that character. Very rarely were they set up with any kind of backstory to make them a person to the viewer or reader. And very rarely did one of the stars say something like, "Ensign So-n-So was a good man. He had a wife, three children, and a family Tribble farm on Rigel VII. He'll be missed. ...So too will we miss the free Tribble meat." Their deaths didn't matter, so of course they became a joke.