And how do you give zero external punishment while making mechanics more difficult? You've been talking about Ozma as a way to put difficulty, but Ozma is literally 4 phase, with 1 or 2 short mechanics that are condensed into basically donuts/chariots, line aoes, and stack markers. The only argument of difficulty is the lack of cast bar for the attack and the speed of it. Which yeah, they have a lot of things like that in extreme without wiping the party
You seem to be forgetting the fact that FFXIV have instant raises that makes any sort of difficult mechanic without zero external consequences is basically a trivial thing. How do you solve difficult mech that doesnt punish players? Suicide it. Why do you think unsync O12S during SHB and EW is using the goodbye hello world strat? Why do you think extreme is still clearable with 5++ deaths?
Your argument of NA is a cultural thing. If you're saying the perception of NA players in PF are that they are unable to think outside of the common strats for something that doesnt need strat, then you're just saying skill issue because as data have mentioned in, JP players have no problem in clearing CAR. even in week 1 when theres no clear strats to use, most of em just wing it. And that is also a weird way of adjusting difficulty. "oh some players cant decide the strat to use, so lets make a content where strat isnt required but somehow we have to make it more difficult".
That is also not a problem of making consistent difficulty. It is HARD to make consistent difficulty precisely because difficulty is SUBJECTIVE and consistency is NOT always the goal to aim for. See how being consistent is shooting themselves in the foot now with MSQ? I rather them play around with variety and sometimes tuning it a bit skewed to the hard side rather than having the same slog consistently.