Hi Pemerton! Can't say I disagree. The ordering of priority Game>Campaign>Players does not feel right to me, although I think there is a valid point in there about not bending to player wishes if you think it will harm the game. But that's ultimately about what is best for the GM and the other players, not the Game as an abstraction.
I do think 1e AD&D is more suited to ignoring & changing swathes of rules than is 5e. I was annoyed by the GM (who had mostly ran 1e) who declared after play had started that Rogues could not Sneak Attack when shooting into melee, since that is a huge nerf to the class which he said was for reasons of realism. Whereas running 1e there are a whole lot of different valid approaches to Backstab.
We should realize too that in those days DM's had campaigns and players came and went.
I am very up front with my players. I will tell you what your characters senses are revealing. The "rules" do not exist to your character. You are roleplaying your character. The degree that rules influence your thinking they are the accepted wisdom of the community. Now it would be insane to say the accepted wisdom of the community completely contradicts reality. How did that wisdom come about? On the other extreme it would be insane for a character to be thinking "That's impossible" as he watches it happen.
And of course this often comes down to an interpretation of a rule. So it's a gray area. Or it does come down to houserules and where it is known by the PCs and not. For example, I do not consider the monster manual or the magic item lists as player knowledge. I'm not stopping them from looking at those things but I am by no means promising to adhere to what is written at all. That is my solution to the old advice that you don't let your players read the DMG and Monster Manual. That has over the years with so many people being both players and DMs become totally impractical. I just tell the group not to trust those books.
If I as a DM, houseruled fireballs from d6 to d4 then of course I would tell them that at the start of the campaign. That is a pretty hokey example but another might be X and Y races don't exist in the campaign world. Or only these classes are allowed.
The game is the rules. The DM if up front has the right to run the game he wants to run. And players have the right to opt in or opt out. Without rancor by me I'll add. The campaign is more about what elements are allowed in the game or perhaps changed. Monsters and magic items for example. If a player says "I want to go find the eye of Vecna", the very first question I might ask "How did your character hear about such a thing?" If they are persistent and no eye of Vecna exists in my campaign world then I just let them waste a few game months rolling dice until they realize there is no eye of Vecna. There is no implied promise of anything in a campaign setting. So the reason Gygax has it Game > Campaign > Characters can be explained this way. Houserules > Campaign setting decisions > Character preferences. Now that greater than sign does not mean always. It means if you are really invested in something that is the order of priority.
I may spend 200 hours prepping a campaign setting (as I run more than one campaign in a setting often). I start building them long before the players know I'm even going to run a game. I am lucky if some of the players have prepared anything at all before they show up. They've got zero hours invested.
Edit:
And to make clear. EVERYTHING is not important. So you when it is not important to you as DM then by all means give the players what they ask for. That is the common case. I'm just saying when it really matters to you the DM then you should take a stand.
Luckily 5e D&D can do that style very well, as well as handling 4e style dramatics pretty well too.
