Just yesterday, I was running Tales of the Valiant (so pretty close to 5e). Unlike 2024e, they didn't improve healing. They gave the classes more bennies and things to do, but there wasn't a significant boost to sustainability, while the monsters, if anything, got fiercer.
They were fighting a CR 4 Weretiger. This is it's attack routine:
Multiattack: the weretiger makes four(!) Claw or Scimitar Attacks. It can replace one attack with Bite if in an appropriate form.
Claw: +5 to hit, 7 (d8+3) damage.
Scimitar: +5 to hit, 6 (d6+3) damage.
Bite: +5 to hit, 8 (d10+3) damage plus DC 13 Con to avoid being cursed with weretigerism.
Bonus-Bleed Prey: choose one creature within 30'. Can pinpoint prey's location within 60'. If the weretiger hits that creature with two melee attacks, they rend- DC 13 Con save to avoid 7 (2d6) damage at the start of their next turn.
So a new player just joined the game with a 4th-level Ranger. 36 hit points, AC 16. Round 1, they ran up to the weretiger, making three attacks (ToV Rangers get a bonus action for two off-hand attacks with no stat to damage when two-weapon fighting).
The Weretiger in turn, uses Bleed Prey on the Ranger. They hit with three claws (on a natural 20) and their bite. I use average damage unless there's a crit, then I roll the damage di(c)e for the critical. So from the Ranger's point of view, this was the turn:
"Take 7 damage, take 7 damage, take 12 damage, take 8 damage. Ok, now make a DC 13 Con save. You failed? (+2 Con save, ToV Rangers are proficient with Str/Dex saves) Ok, that's 7 more damage."
"....I'm down." The Ranger's player makes a sad face.
That was it, that was his first combat round. From full to 0. If the monster could kill him at 0 hit points, he'd be dead. No warning, no nothing. No opportunity to do anything about it, make a new character. The party would get him up with minimal hit points (even a level 2 Cure Wounds from the Bard is only 2d8+4, the Ranger's own Cure Wounds is d8+3, and the Bard's performance allows you to spend a Hit Die to heal with a bonus equal to the Bard's Charisma, so that's 1d10+6 in this case. If all of those are used in the same turn, the Ranger isn't even back at their maximum hit points, and the Weretiger has demonstrated the ability to bring them from full to 0 already. So the melee Ranger was forced to disengage, drop their short swords on the ground, and switch to their longbow and deal d8+5/2 (because of course the weretiger is resistant to non-magical attacks) instead of using their +1 short sword for the rest of the combat. Because using the party's limited resources to keep healing him back to full only to have the monster decide to kill him again really wasn't worth it.
And that was kind of how it went for the rest of the session. A fight with some Death Dogs, a brawl with a Minotaur, the final battle with a CR 5 Sorcerer...every time he got into melee to do his Amazing Ginsu routine, the monster would see him as a threat, unload their damage on him, and he'd be on the ground bleeding out again.
And you can't even say he should have switched Con and Wis for example- all he'd have gotten was 4 more hit points.
Now some people reading the above might say "good! Low level characters should drop like flies! They need to be more cautious! He should have known better than to attack a weretiger head on!" and honestly, if that's someone's preferred style of gaming, that's great.
But this is what I keep seeing in 5e (and 5e-alikes). Almost no interaction between "player healthy" and "player critical" when it comes to combat. And no ability for a player to gauge "hm, can I afford to attack the monster and not die?" until after they've seen it tear large bloody chunks out of them!
So yeah, a good "death buffer" is fine by me. I don't want players to die due to actually thinking they can enter melee combat.
*Plus, in this particular circumstance, if I really wanted a character dead, with four friggin' attacks, downed PC's have zero chance to survive.