This is the problem with the level of overhead involved in taking wotc up on the simplified for rulings not rules & to let each table customize it to fit the kind of game they want to run. The system needs to be built to support that from the start & the state of the dmg optional rules shows just how much of an afterthought it was. even simple things quickly start spiraling into the depths of "is this still d&d 5e" because there aren't enough hooks, things from past editions that would enable aren't even listed as options*, & frequently the system is coded against doing that.I don't think "GM decides" is a rule that can be meaningfully interacted with — it's not a mechanic that provides gameplay the way negotiations for P/E in Blades, or choosing my options in a PbtA does.
In an imaginary PbtA game, imaginary move "SKULK: when you sneak quietly in the shadows to get somewhere or gather information, roll +Sneak. • On 10+, choose two: it didn't take much time — or — you didn't leave a trace behind — or — you still have a way out. • On 7-9, choose one." is gameplay in of itself, and more importantly, it gives me clarity and structure, whether I am GM or a player.
"The GM will tell you what to roll and your DC (maybe by consulting on some table somewhere) and then will tell you what happens next" doesn't give me neither
That's actually poses a very interesting question worth discussing.
At which point we actually stop playing D&D and start pretending that we are playing D&D?
It's very clear with, say, Dungeon World. If I'm running a murder mystery set in an absolutely mundane vaguely medieval city, where the PCs are hunting for clues and piecing together a puzzle, while not being in any danger themselves, I'm not running Dungeon World anymore:
It's pretty obvious, and undeniable — at best, I'm running a hack of Dungeon World with different Agenda and Principles (even if they are not formulated), at worst I'm fooling myself and everyone else.
- I'm not playing to find out what happens — the important things already have happened and the main thing is figuring them out
- I'm not portraying a magical world
- I'm not filling the PC's lives with adventure
* which I guess puts them in the same state as the unsupported "optional" feats & magic items minus actually having any ink or pagespace devoted to them