I think I also agree, but I would include the caveat that the game designer should be doing most of the work. They’re going to provide the procedures, principles, etc that allow the GM to run the game in a way that keeps things honest. After that, you just have to make sure you execute correctly (which admittedly is not always easy, especially when trying new games).I think I agree with you, but this very much sounds like the "design a board game, and then describe fiction around it" approach. You have to do a lot of work if you want the board state to keep presenting interesting choices and remain consistent.
I’ve linked a few reports already, but there are others in the five words commentary thread.I obviously don't know your game obviously, but the problem I usually see is either that the board state presents trivial optimization problems (which are generally not even considered as optimization problems for narrative reasons) or you lose a degree of optimization by not allowing the players to avoid failure points. That is, the players declarations are fixed in relative time, thus that whatever they do will have an equivalent impact (or if we're talking variable completion, an equivalent magnitude impact) on the outcome. Consider trying to break into a castle using skill checks based on objective DCs, vs. a flat skill challenge to do the same thing. It is possible in the former case to present a course of action that calls for more or less rolls, and not in the second, even if the resulting fiction between the two is otherwise identical (admittedly a really unlikely and probably contrived scenario).
The gist of the system is it started out as a hack of OSE and WWN that evolved into its own thing. Skill checks are versus a flat range1. Skills ranks range from +1 to +5 (−4 for untrained) and attributes go from −3 to +3. Rolls are 2d10 (10−/11–16/17–22/23+ for Failure/Mixed Success/Complete Success/Critical Success). The reason for doing things this way is to reduce or eliminate the places where I can put pressure on the game unfairly. When there is a Failure and Mixed Success, I get to apply consequences. Those should be communicated up front (which is something I admittedly could do better), so players can reason about their course of action. Players do decide the method (skill) and approach (attribute), but it has to make sense in the fiction. The plan is for skills to have scope for what they can do, so you can’t just Burglary to persuade someone no matter how much better it is than your other skills. I don’t have skill challenges, but I do use clocks.
I would use a combination of approaches to handle the proposed infiltration scenario. The basic play loop handles time very concretely (10-minute turns while exploring). You can only travel so far or do so much in a turn. When the PCs encounter a situation they want to change, they can make Skill Checks. What’s appropriate will come down to the situation (e.g., different skills are appropriate for convincing someone to let you through versus picking open a locked door). Depending on how they roll, there might be consequences. If the scope of what they want is too large for a single Skill Check, I would put it to a clock (e.g., post #202 where the party tries to convince Old Gregg to give them information). Clocks can also be consequences (like a clock to track guard alertness). If the alertness clock goes off, the guards’ presence will increase, making the infiltration more difficult. Being a player-facing and manipulable mechanic, the players can try to push it back by taking appropriate steps, but failure could also pull it forward. There are trade-offs and consequences.
Anyway, the players get through the castle however they get through the castle. I’m not beholden to a particular solution. If they get into trouble, they have ways to navigate it (including straight up fleeing if necessary). The idea is to set up the situation then see how things play out. The mechanics facilitate that by letting me respond as strongly as the situation demands (you snuck into the castle and murdered the duke, therefore guards!) while avoiding the problems that come from having responsibility for setting the scenario, adjudicating it, and deciding how and what consequences there will be.
It seems like concern here is about maintaining causality and having strong processes for play. Objective DCs are one approach that works because they allow players to reason about outcomes. If the DM can decide, that creates risk of impropriety (e.g., pushing the outcome in a desired direction) even when none is intended.The appeal of a simulationist model is that actions naturally move the player different distances toward their objective, and do so without any risk of someone tweaking the board state, which gives you at least two axes to plan lines of play along: how many failures points, chance of success at any given point and then likely more (resource expenditure, severity of board state at failure, etc.).
[1]: Except for attacks. Everything uses the same basic math, but attacks are made versus Armor. It still has the same ranges of degrees, but creatures and PCs have different Armor values depending on proficiency and gear and whether they are using Dodge, Block, or Parry. In combat, the Mixed Success result is (typically) to do minimum damage.