Oh please. I run keys ranging from 11-14 on 6 different 120s every week and I see those types of players, the kind who expect MDI executions in at least 50% of those. And that is keys I list myself or the ones i join on the group finder.
The "fast run" or "big dick dps" keys don't even factor into this discussion. Where's the logic in that? Those keys clearly advertise the use of MDI executions.
The cases being discussed in this thread are the kind where "leavers" seep into normal keys, based on 1-2 "fails" (using the term fail loosely here). But sure, way to try and take the discussion off track to suit your own narrative and come off smug based on that. Sigh...
From personal experience, more often than not, folks who leave keys fall in the 1.4k-2k Rio score range. The reason they usually leave range from wiping once or twice to "otherwise easy" pulls (relatively speaking) to the party lead or the tank/heal not doing things the way that player expects it to be done, even though they really have no place calling the shots.
The best examples, ones that i've genuinely laughed out loud IRL as a result, are when tanks/heals fail a mechanic and quit due to embarrassment. Happened to me in a shrine 13 where our 2.5k rio tank died to aquusir's Surging Rush, and then proceeded to leave the group without saying a word.
None of the examples I've just given based on my own very real personal experience fall under the narrative you concocted in your head.
The problem of leavers in M+ is real and is almost a by-product of the Rio site/addon themselves, because nobody from a particular subset of M+ wants to see a potential untimed key on their Rio profile/page in Keystone history. Rio has to step in and take responsibility for this. Plain and simple.
Blizzard disabling support for the Rio addon in their API would give us the best and most clear picture of whether the "leaver" culture is inherent to the M+ system itself or because of arbitrary metrics created and tracked by players themselves.