The only time it damages the plot, is when Oda plays the the actual death card, and then undoes it. It's fine for someone to fight till they are unconscious, or nearly dead, and then be fine later. It's shonen, that's part of the agreement.
But when he does things like say "the one prisoner bit off his tongue to avoid going into slavery", and then give it a moment of silence and respectā¦ only then to have him up and kicking a chapter later in the background, it affects everything.
Its a problem when Oda plays it as a dramatic cliffhanger like right now with Sanji. Yeah, we know a main character isn't going to die offscreen... but we know even if we get a 20 chapter flashback starting next week, he's still not going to die then either... so playing the card where everyone is stewing and crying over his loss is just insincere and feels false.
When Sabo is supposed to be assumed dead, and we know it isn't so BECAUSE there was no drama. When Oda tried to do a fake out on the Franky Family dying that no one believed for a second. WHen one of the horses storming Enies Lobby is shot in the heart, but is fine later. When Monet a super graphic death that should be conclusively dead but still leaves a blatant out for her to be fine at some later point in spite of the drama. When Enel destroys an entire island and no one is hurt, includign Pagaya who had been offscreen for a year. When Bellamy comes back from being executed a decade later. When the great war apparently only had the two casualties out of the entire mess (and maybe Oars Jr.) instead of hundreds of people dying. When Doflamingo shreds an entire city with zero casualties.
That's when Oda's playing loose with death weakens the story, and its an unfortunate weakness. It makes the villains less villainous, and the heroes accomplishments less heroic. When any shmuck on the street can survive being exploded, shot, and then peed on, it stops being amazing that the hero can do it too.
(I'm actually okay with Pell, because he was a heroic character, who still thought he was going to die, and was mourned, and that was a small one time saving grace... but then it kept happening.)
If he doesn't want to make death cheap by not having it be permanent, if he doesn't want to kill characters when their death serves no point to the overall story that fainting serves just as well... that's fine, that a choice he makes. But then he shouldn't be playing the actual death card by pretending.