This is the thread that finally got me to delurk and post something. I started doing tabletop gaming in the late 70s, though a lot of what I'm going to describe happened more in the early 80s. Here's a few things:
Hardcore mode. Gaming was intense, and characters died. A lot. Dungeons could be brutal and horrifying. But just like a fish doesn't know its wet, we weren't particularly conscious of this. It was just how it was. Having a high level character was a point of pride because it was difficult to achieve. One GM in particular had a jar full of ashes. If your character died during one of his games, he'd take your sheet and burn it on the spot and put its ashes in his jar. There were a LOT of ashes in that jar.
Fewer Campaigns, more one shots. The campaigns that were to be had lasted a long time. One lasted four years. Mostly we did one shot adventures with rotating GMs. Everyone would GM a little, and you'd have a roster of characters you'd run through adventures slowly leveling them up. The adventures weren't particularly well integrated into one world, we just didn't worry about that part. If a character died in one of these adventures though, they were DEAD, and it was very bad form to play them again. You had to be really careful what character you used in who's game, especially if the GM had beef with you. You'd typically have five to fifteen characters in your roster and keep playing them in multiple adventures with multiple GMs.
Slow Leveling. These days it feels like you can level three times in one adventure! That was definitely not the way back then. You could play through three four or even five adventures before finally getting enough xp to reach the next level. This built a lot of attachment to each character, at least for most of us.
Rampant Poorly Executed Cheating. Things were hard, and people compensated in a variety of ways. Its nice that everyone likes to image we were all super skilled awesome players that were a hundred times more hardcore than the punks these days, but no, really most of us just cheated ridiculously. There were a few people who had characters with stats of all 17s and 18s, and max hit points rolled every level. There were guys who would roll their dice and then scoop them up into their hands before anyone could see the numbers, then tell us what he rolled. Shockingly he rolled lots of 20s. We caught people with loaded dice. Who brings loaded dice to a D&D game? Players would lie about the rules and try to trick the GM. There was a distinctly adversarial relationship between GM and players in our little group that got frustrating for me on both ends. Also considered cheating: keeping multiple copies of your character sheet so you could keep playing a character when it died.
Lots of House Rules. Every GM had a few. This was easier because frankly the 1st edition rules were a cludgy mess. No part worked with the others particularly well so it was not hard at all to add new systems, replace old systems with your own, etc. It actually made the rules very modular and customizable. In hindsight that's actually good but at the time, I hated it, and I was honestly shocked when I learned there was an OSR. I had so many house rules trying to correct the many problems I saw in the rules.
Christians Hated D&D. Seriously, its probably hard for people today to imagine, but Christians were the SJWs of the 70s and 80s. I kept D&D books and supplies for several gamers whose parents thought D&D was literally devil worship. It was a specter hanging over our heads at all times. I mean, 2nd edition completely removed any reference to demons and devils in trying to placate these people. There was a serious cultural backlash against playing D&D, which ironically made it edgy and cool. Once normal people figured out that no, its not edgy and cool, but in fact something mostly geeks play, games like Vampire, Cyberpunk, Shadowrun, etc showed up as if desperately chasing the edgelordiness D&D had lost. Coincidence? I THINK NOT! And about that removing demons and devils bit... that same atmosphere is present even more so these days just the humorless scolds have changed.
A sense of accomplishment. There was a huge sense of accomplishment for making a character, playing by the rules, and succeeding in these admittedly tough adventures. In particular I had this shitty little thief character that started with a whopping 2 hit points that I played through a lot of these random non campaign one shots, usually with characters with all 17s and 18s and max hit points. The thing is, you don't cheat if you don't have to. I played smart, as the games those days demanded. The ones who cheated didn't play smart and tried to just bull right through everything. Invariably, my crappy little thief outdid all of them by quick thinking and creativity. I survived not one but two party wipes, and some of those guys playing the cheater characters even tried to kill that crappy little thief when they were GMs, and failed every time! That crappy little 2hp thief wound up as a Thief/Fighter/Mage with probably about 20 levels scattered out between those three classes, and ended up being arguably my most successful character. Its hard to have the same attachment to characters these days. I don't typically stay with one character for four years, or take four years to go from 2hp scrub to 10th level hero like in some games at the time. It changes how you play and think of your character and the game.
Anyway that's it, my random meandering thoughts. Hopefully this was interesting.