What's the alternative? How can multiple people always reach consensus on context in a game that takes place largely in the players' imaginations, and where many people don't want to have control over anything more than their own character?
I don't know what RPGs you're familiar with, so I'm not sure if these examples answer your question: I would point to DungeonWorld, Marvel Heroic RP, HeroWars/Quest, and many similar games.
Not to mention 4e skill challenges. (Which are very different in resolution technique from 4e combat.)
These games have systematic ways for establishing consensus over the fiction (with the GM taking the lead), and for allowing players to bring their PC build featurs to bear, without the game breaking. (Not to say they're necessarily perfect - but they show how it can be done in a reasonable, functional way.)
(Also - they're not the only viable form of RPG design, obviously. But I think they answer your particular question in the context of this thread.)
I don't understand/disagree with this. Ambiguous rules require rulings. The need for a decision is implied by the non-specificity of the rules. One can detest that style of rules writing, and still appreciate that it accomplishes the intended goal--letting the DM decide.
I'm assuming you've anticipated this response and have a counter-argument ready. I'm jumping in because I'm genuinely curious as to where you're coming from, and would like to see you respond to a non-hostile phrasing of (what I consider to be) the obvious objection.
The thing is, to me, the rules
aren't non-specific. They are several hundred words. And interact with various mechanical subsytems like elven and halfling special abilities.
If the idea is to let GMs decide, why not say something like "If you attack from hidden you get advantage. You become hidden by making a successful Stealth check. To make a Stealth check you must have sufficient cover/concealment that your enemies can't see you. You remain hidden by not exposing yourself to your enemies (by sight, noise, smell etc); if in doubt compare your Stealth result to the enemy's passive perception."
Then halflings could say something like "Because you are small, quick and lucky, you can hide behind your larger friends." And elves could say something like "Because you are a fey creature of the wilderness, you can hide in rain, snow and long grass."
Those rules would be non-ambiguous. And would give the GM power, under the assumption typical to D&D that - if in doubt - the GM has authority to adjudicate matters of fictional positioning.
It's obvious that there are methods other than rules ambiguity to force a DM decision. How does this make Mearls wrong when he says that the ambiguous rules text is a call to let the DM decide?
My main framing for thinking about rules drafting and interpretation is legislation. A poorly-drafted at can force judges to make creative interpretive decisions. I don't think of this as the same thing as an act which expressly confers discretionary or interpretive power upon a judge.
stealth is extremely hard to calculate and implement in a simulation.
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For those with strong objections to the 5e approach, please point to a workable ruleset that does not need 'common sense' interpretation at the table
No one is objecting to "common sense" interpretation being required, that I can see.
And my point is that there are better and worse ways of writing rules to support GM adjudication of fictional positioning via common sense. If the idea is to prioritise fictional positioning over technical rules concepts, then writing hundreds of words of rules that obssess over technical rules concepts isn't the way to do it.