The Crimson Binome
Hero
Moreso than any other edition, AD&D was a time where your experience was going to vary heavily between tables. No two DMs ran AD&D the same way, and since there was no internet yet, it was impossible for everyone to come to a group consensus on anything. It was probably the last time that a DM could get away with using significant house rules, and players would willingly accept them, since every table had them and there weren't a ton of alternatives.Well, actually they didn't really. My memory of od&d and ad&d is one where I can't remember the name of any character I played, because becoming invested in a character was a futile exercise. Life was cheap, and characters survived more through luck than through having control of their destiny.
I will say that the penalty for death did backfire in at least one way: Since dying was so terrible, it made many players too paranoid to do anything for fear of failure, which meant that some DMs turned to paranoia monsters that would kill everyone regardless (see your first point about it not being the player's fault), since that was the only way to challenge a player who was unwilling to take unnecessary risks. If you're unwilling to charge the ogre, because it might kill you, then every treasure chest is going to be a mimic full of rot grubs. It was a vicious cycle.
By making death an acceptable consequence, at least it encourages players to engage with enemies, so that you don't need to resort to rot grubs everywhere. Of course, I would argue (and the premise of this thread is) that they've gone too far - the consequences of combat are too trivial, and even the worst-case scenario is recoverable without much hassle. Fifth edition is a time where I can't care about any character I play, because it feels like none of their actions have any consequences. The only consequence which is more than trivially inconvenient is a TPK. It just doesn't feel real or believable for me to not fear the giant monster, because I know that it can't really hurt me in any way.