I don't have time to engage with any posts (nor the large ones I've been tagged in), but I do want to say a few brief things. No I don't think that people who believe that they are engaged in Sim-Immersionism are delusional. However, I will say that my concerns lie in the following, regardless of play agenda:
* Interrogation that leads to directness and brutal honesty with one's self about both the actual, moment-to-moment machinery of play and the overarching agenda that informs that machinery.
* GMs are making decisions all_the_time. All the time. It doesn't matter whether you're running premise-intense & situation-sensitive Story Now play in the vein of Dogs in the Vineyard, My Life With Master, Agon...or Story Now play with intuitive, snowballing continuity of malleable myth like Apocalypse World, D&D 4e, Burning Wheel...or something in between with intense sandbox inclinations like Blades in the Dark, Mouse Guard, Thousand Arrows. Or a variation of Trad 5e; Hickmanesque GM Storytime underwritten by Ouija play or Sim-Immersionism featuring Setting-As-Protagonist (SAP?) like a Trad FR sandbox or a 5e Adventure Path or some combination of any of the prior three with PC arc preconception/Power Fantasy becoming situationally prominent/featured (NeoTrad). Or a B/X pawn stance dungeoncrawl or hexcrawl.
What matters is that (a) all GMs, regardless of agenda and procedures, are making decisions all the time and (b) no GM ever is interested in straining credulity with causality-defying situation-framing, decision-space management, or consequence-space rendering.
* So what are we left with? We're left with "why am I making this decision right_effing_now?" I can give you the train of thought embedded in every_single_decision I've ever made as a GM:
1) "Is this an engaging decision-space featuring compelling (for the game-relevant value of compelling) situation and a multivariate consequence-space that provokes and demands thoughtful, rigorous play and assumes robust rules and related handles; put another way, is it richly gameable?"
2) "Is this content premise relevant?"
3) "Is this content genre credible?"
4) "Amongst the myriad of options availed to me which are all credibly, causally downstream from prior fiction, is this situation-state (framing or consequence) plausible?" Choosing the most probable is absolutely absurdist...as if I (or anyone else) is possessed of the mental bandwidth and cognitive toolkit necessary to determine probabilities in complex systems approaching any level of precision...and if, on rare occasion I feel one situation-state is marginally more plausible than an alternative, I'll always defer to the one that leads to maximal integrity of play (which will be system and premise-indexing), hews toward invigorating/provoking in its elements rather than sterile/conflict-neutral, thereby passing muster with 1-3 above.
TLDR on the above, assuming both are plausible, I will never defer to sterility in the case that I'm possessed of a level of comfort that one situation-framing or state-change bears out some minor level of plausibility over another. I'm quite lucky that I don't even think like that so all I have to worry about is the flow-chart of engaging/compelling/rich > premise-relevant > genre credible > causally credible? My flow chart isn't the inverse where I'm examining causally credible first > sifting via some very-back-of-the-envelope, personally imagined subset of most credible > if that state-change governed by most credible isn't rich with consequential action, provocative, and conflict-charged, simply ride-it-out until that loop eventually churns out a moment approximating that.
5) Following from (1) above, "how do I best manage the technical and experiential divide when I'm very learned on something relevant and the players I'm GMing are not (something like climbing, outdoorsmanship, or martial combat)? How can I use the system's User Interface (rules as common language which help generate mutual understanding) to compose and articulate a gameful space where the players are endowed with a decision-set that they can well-understand and then operationalize?"
TLDR and hopefully it is clear. I'm a Game Master. I'm running a game. Each game has distinct characteristics (premise, agenda, procedures, superstructure, participant principles, authority distribution, incentive structures, currencies, advancement scheme). No matter what game I'm running, no matter how many games I'm running at one time (not in the same moment, but weekly games), I want every decision I make to be..."game-forward." Yes, each game includes characters and settings and myth and motivations which endow play with meaning and momentum, but I'm wholly preoccupied by the effort to generate for my players the best gameplay moment possible in the game they're playing...right_now. And I want to stack those over and over until we're done.
I will never choose a sterile or mild or tepid moment of play for some notion (of which only I will overwhelmingly be privy to) of "enhanced causality," when an alternative choice is more engaging and provocative. And I will never feel like I (or my players) need to endure moments (perhaps even many!) of conflict-neutral or sterile play in order to "pay for" conflict-charged play later (and please let us not pretend that we haven't seen this all over the place here and elsewhere...that train of thought is ubiquitous..."if everything is cool, then nothing is cool" is one formulation of that absurd take).