ExploderWizard
Hero
This is apt. People joke about the Gygaxian dungeon master, but it is very true that in early D&D the dungeon master was encouraged to be far more objective than he is today, and players came to the table with less of a sense that they were in starring roles.
I don't mean to pass judgment -- I am intentionally and very carefully avoiding the use of the word "entitlement" -- but campaigns from late AD&D2 on have been "about" the PCs, where as previously they were "about" a crisis, which the PCs then resolved.
Character death is a great example of the changing state of play -- today it's a huge bogeyman, but back in the day death was just part of the job. I don't think players were less attached to their characters; there was just a better sense of perspective. The party's success was your success.
I think the overall shift is more about expectations of play due to game presentation than player entitlement although the former feeds into, and tends to create, the latter.
I think that D&D as always been "about" the PCs and very player focused from day one of OD&D. Unless large portions of the game are run that don't involve the PCs I don't see how it could be any other way. What has changed is the whole approach to D&D. I approach and enjoy playing D&D as a game. I play for the fun and to find out if I win or lose. Unlike other games, when you lose at D&D the game doesn't have to end. You can quickly generate a new PC and continue playing. Approaching D&D as a storytelling exercise is something that came later. In this approach, the characters are actually protagonists and the "game" is about telling their specific tale. Under this approach character death throws a wrench into the flow of the story and is avoided as much as possible. That take kind of ruins the game aspect of play that appeals to me. If I'm playing to see if we as a party, can win or lose and the whole process shifts to becoming merely all about how we win then I no longer see the point of the experience of playing a game. I can still see it as a fun experience of its own but it doesn't scratch the same itch as actual gameplay in much the same way that a boardgame doesn't fill the role of playing an rpg.
The largest shift in style from early D&D to later was the role of the actual player in the game. The earlier in the lifecycle of D&D you go, the more the capabilities of the player impacted gameplay. Using the plain old fighter as an example, in OD&D the mechanical difference between a 10 STR fighter and an 18 STR fighter largely amounted to the 18 STR fighter gaining a 10% bonus to earned XP. Thats it. Keeping the character alive was the player's job. The challenge of gameplay was for the player to enjoy. The concept of challenge to set of values on a sheet came later and I still don't see how that is possible to this day. A set value vs a difficulty will result in some probability of success which is then rolled. The luck of that roll determines success. The player does his/her best when building the character to make the probabilities of desired activities as favorable as possible. Thus most of the challenge for the player is over before play begins.

Preferences being what they are, everything hinges on what you are looking for from the experience.