I was hoping that one of the things that the work of Peterson, et al., would do would be to curtail the essentialist narratives.
Early D&D was just as (if not) more diverse in terms of approaches and playstyles than we have today, depending on when and where you were. It was not just about "beating a dungeon, and was more viewed as a toolkit to enable play in the 70s. It is simply error to try and incorporate our views from today back then; even people who grew up playing in the 80s have a very poor view of what the game was like in the 70s.
In other words, most of this just isn't true. The Elusive Shift explores this in more depth, and there have been numerous threads on the subject.
Meh, I speak from experience, I was there. Not in the 'Ur Games' of Gygax or anything like that, but I played in D&D games starting around or even before Greyhawk. I agree, nobody can rightly say that it was done in 'one way', but I don't agree that there was as much range and diversity of play as there is today. And while there were some vocal champions of various things, as I went around the country in the last 70's and early 80's what I found at the tables in the schools, Boy Scout Troops, FLGSes, and friend's homes that I played in was, there was not that much characterization in general. Nobody really asked what the motives of a PC were, or how the events of the game effected them, not really.
Heck, I remember my friend started a campaign in around 1983 with 1e. For some reason I got in some solo play at the start, and he set me up with a Ranger, and 2 other PCs which are long forgotten. I ran into some sort of 'zealots' and they ended up murdering the other 2 PCs but the ranger got away. So, after he found out who these jerks were, I got dispensation to make them his 'favored enemy' instead of getting the bonuses for humanoids, I got it for killing Demogorgon worshipers. Forever more after that I played that character as being bent on exterminating Demogorgon from existence. He was so fanatical he eventually got to be 12th level or something like that, and by then he was batshit crazy, more vampire than ranger, and he finally got to slay Demogorgon! That was really the first that I remember of anything even close to 'character development'. There were other similar things going on with other players, but it sure wasn't that common and it rarely ever happened in the 70's, back then people were just amazed by the very concept of an RPG at all, that you could declare ANY MOVE and not just something someone else coded into the game. That was RP enough for us in the early days.
Again, I am not saying this was universal, and there are well-documented cases of people doing heavy RP, but the chance that you could throw a stick at random and hit THAT table, it was small.