I guess they had their place in the founding of the game and what it was designed for, but the expectation in D&D nowadays is that a character is more than a collection of stats and gear on a page but a living, breathing character with motivations and flaws and relationships. Not to say this didn't exist in the days of dungeon crawls and death traps, but it wasn't nearly as central to the game. Quick, cheap deaths brought upon by Save or Die effects, no matter how well telegraphed, are entirely antithetical to a game that values rich, complex player characters.
The game does not need Save or Die to create tension, fear, and the legitimate danger of death, and I would argue that being successful in that without using cheap, single-roll spells or monster effect creates much richer and stronger tension & fear that feels far less artificial.
I mean, do what works for you, of course. Personally, I think the statement that Save or Die would be a terrible design flaw is the only correct one in regards to modern D&D.