Did you play AD&D? I can't remember how old you are, so hopefully that's not too offensive. If so, was a typical game really as hostile as people say it was?
That's one of those question where the answer hovers somewhere between "no, with a couple of massive caveats" and "yes, but not in the way most people think".
A lot of AD&D 1st Edition's GMing practices are pretty hardass by modern standards; however, they need to be understood in the context that the game's authors were writing for a target audience who mainly played the game in college wargaming clubs, where players would frequently transfer between groups and group sizes tended to be very large – six players per GM was considered a bare minimum, and up to a dozen player characters in a single party was by no means unheard of!
In particular, players would often bring their character sheets with them when hopping between groups, and it was considered a faux pas for a GM to reject an incoming player's existing character or request any substantive changes be made, so managing expectations could be quite challenging; even as late as 2nd Edition, the Dungeon Master's Guide contains extensive discussion of how to gracefully handle players bringing existing characters with them who aren't necessarily a good fit for the present game's tone or resource economy.
The upshot is that the culture of play these iterations of Dungeons & Dragons are targeting inherently obliges the GM to take a much firmer hand to keep things on track than a pickup game that draws players exclusively from within the GM's established friend group might – and to be sure, some GMs abused these expectations to act like petty tyrants, but some contemporary GMs do that, too.
A big part of the modern perception that 1E and 2E were extraordinarily player hostile, meanwhile, has nothing to do with the previously discussed GMing practices; rather, it emerges from the transition away from that culture of play in a slightly unexpected way.
In brief, back when D&D was mainly played by wargaming clubs, it was fashionable to run pre-written adventure modules competitively at conventions; the competition wasn't between players, but between parties, with multiple groups running the same adventure in parallel to contend for prizes. Tournament play sometimes chose its winners based on the fastest real-time completion of the module in question, or set specific objectives within the module which would award points when completed, a bit like speed-running or achievement-hunting in a video game (though neither practice existed yet at the time).
It was the survival module, however, that quickly emerged as the most popular tournament format. In a survival tournament, each player would provide or was furnished with a binder containing a fixed number of pre-generated character sheets, switching to the next character sheet in the set as each preceding character died; the winning group was the one whose last surviving character's corpse hit the dirt furthest from the dungeon entrance.
Many of 1E's most popular adventure modules, including the infamous Tomb of Horrors, were originally written as survival modules to be run at tournaments in conventions. As such, they were designed to kill off player characters both quickly and efficiently, so as to reduce the likelihood that the tournament would run overtime and get kicked out of the convention venue. When they were later cleanup and repackaged as commercial adventure modules, their text rarely bothered to explain any of this – who doesn't recognise a survival module when they see one?
The answer to that question, of course, is kids who didn't come up through the mentorship system of the college wargaming clubs, but taught themselves how to play D&D from first principles using books they bought at their local hobby stores – and when D&D's popularity unexpectedly exploded in the early 1980s, there were suddenly rather a lot of them!
These kids purchased the repackaged survival modules along with all their other D&D books; having no frame of reference, they assumed that these represented what a "standard" D&D adventure was supposed to look like – and since they weren't experienced players with whole binders full of pre-generated backup characters at their fingertips, the result was a lot of seemingly unfair total party kills, and a lot of kids concluding that the previous generation's GMs must have been objectively insane.
