If the players see their characters as protagonists in a story, why wouldn't they expect their characters to have at least as much protection fro actual death (plot armor) as protagonists in a novel or movie or TV show?I find it odd that some players would want their characters to be immune from death yet 5E has the most death friendly Ress spells of any edition.
Revivify is a 3rd level cleric spells and by the time heroes are that level 300GP is fairly trivial. Plus if your DM is so set on keeping them alive, scrolls etc of Revivify can be sold or found.
If you want to argue the players shouldn't see their characters thus, I'm not inclined to disagree all that hard: I think those sorts of expectations miss the differences in the media. It is, however, a different point than you seem to be making.