I suppose someone could assume that every DM in the world should run the game exactly like every other DM, but that would be...odd, to say the least. More likely, a person playing several games under several different DM's would see the beauty that is RPG's: Diversity in tone, style, attitude, rules, substance, humour, seriousness, and everything else. Eventually, over time, a Player will understand what they know they like and what they don't, and then seek out DM's that provide that "style" of play...or be bold enough to take up the reigns of DM'ing themselves.
Like most things it's a balance. The clearer and more consistent the world the better the players can interact with it. The more rulings the more you can make things your own. When you say "Rulings
not rules" you are making the quite explicit statement that you don't care about any such balance - and that everything is DM fiat.
But no matter how you slice it, DM'ing isn't formulaic. It's MUCH more "art" than "science" (when being run; when doing all the leg work behind the scenes, it's more or less equal). No player needs to 'read the mind of the DM' unless that Player is under the impression that his job as a player is to "outsmart and foil the DM". That's fine if that's the tone of that particular table, but, for most tables I'd guess, that's not the base attitude of a Player. That attitude tends to be "All right! Lets roll some dice and do some roleplaying!".
Roleplaying requires being able to visualise yourself as being in a given world. Knowing what the rules of that world are and the likely outcomes of your actions make it far, far easier to roleplay. A "Rulings not rules" - in other words an attitude that the players can't actually know about the setting other than through what the DM condescends to drip-feed them and setting constants might not be is actively inimical to roleplaying.
So is being utterly rulebound and trying to use the rules as a physics mode. I'm not saying "Rules not rulings" is better than "Rulings not rules". I'm saying if you want to play freeform go and play freeform and discard all the advantages that rules give you and stop weighing people down with rulebooks. Or if you want rules light go rules light (and leave any version of D&D with a PHB at home).
Dungeon Mastering, at it's core, hasn't changed since the beginning, IMNSHO, at lest not very much at all. The Players expectations of their 'role' in the game most certainly have, however. Players used to expect to die. Often and repeatedly. Players saw playing the game as a challenge and a test of their intellect and ability to work together and 'think outside the box' in order to keep their PC's alive.
First, I'd say that if player expectations have changed then so has dungeon mastering. A big part of the role of the dungeon master is table dynamics.
Second it depends what you mean by "Dungeon mastering". I don't run 4e the way I run Rules Cyclopaedia D&D (I refer to RC as "Dungeons" D&D and 4e as "Dragons" D&D with other editions being in many ways somewhere in between, although oddly enough it's at these two extremes where skill is most important the way I run it). And I certainly don't run either the way I run Apocalypse World; the role of the MC is very different.
Alas, I think this is a situation where your idea of a "good game" and mine are not lining up. This is fine, even good, actually. It means that RPG's can be interpreted and played by a HUGE range of people with different desires and preferences.
Possibly, although I've a wide range of preferences.
I've never played Fate, although I did do some "solo playtesting" of it when the guy was writing it waaaaay back when (yes, I'm old; in fact, I probably have the text file on a floppy disk somewhere!). I thought it had potential, I just wasn't sold on the 'simplicity' of the ranges (at least in those early drafts, iirc). Maybe I'll look into the latest version to check it out... a sort of "blast from the past" for me.
Are you thinking Fate or Fudge? Fate 1e was published in 2003; floppies had almost disappeared even by then. Fudge (from which it borrowed the dice and the ranges) was developed on Usenet and published in the early 90s and will have been when the ranges and the ladder was talked about. The big tech in Fate isn't the Fudge dice and ladder, it's the aspects.
I initially thought I wouldn't like Dungeon World (just bought the PDF first), but eventually I dove into it for a third time and something just 'clicked' with me. So I bought a half dozen hard copies for the table. Every game I've played of it (as DM), have ALWAYS been memorable and fun! Then again...I run most of my RPG's "fast and loose", so Dungeon World wasn't so jarring as I've heard from DM's who are used to something like 4e or Pathfinder! LOL!
I don't find Dungeon World anywhere near as good as its Apocalypse World progenitor, so if you liked Dungeon World I'd recommend giving it a look (although Vincent Baker's prose can be overwrought). And the way I run 4e it's faster and looser than any other version of D&D that either has a DMG or uses a battlemap.
I don't honestly think we're as far apart as you think in many ways. I just consider the "Rulings not rules" mantra to be toxic and
at best a response to poor game design where the rules are not fit for purpose - whether because the game is rulebound or the rules themselves are broken.