Unfortunately, as was stated by some people earlier in the thread, a lot of players are averse to any sort of skill expression/skill ceiling. The penalty for positionals is absolutely minimal- we're talking 1/2%- but some people feel "punished" because they either can't execute them or can't be bothered to put in the time to learn how to do it. That seems to be the crux of it.
Positionals actually fulfill two roles quite well- they add a layer of skill expression/raise the ceiling without being too punishing and they add a bit of depth/fun to the melee dance, either by figuring out how to safely land them or plan your True Norths. It's really one of the most innocuous ways of achieving both things... but this is FF XIV, so here we are, for the 100th time, discussing that they should be removed because some people "don't like them" or "feel punished".
You've addressed it yourself, but the argument it leads to more interesting jobs/encounters seems to hold no water to me- you can design a job and then add positionals on top changing nothing about it. Same for encounters. By seeming everyone's admission, missing them isn't a big deal, so they don't even need to factor into... anything really.
I agree with everything you're saying, but you're not gonna get a better answer out of positional detractors- it boils up to a combination of "I don't like this mechanic", "I don't like this allows for people to play better than me" and "it will, somehow, lead to better jobs/encounters".
It's exactly because the reward is mostly negligible that positionals are fine. I can see an argument that a mechanic that slashes your damage by 30% and a beginner can't tackle might be problematic (although I actually think some jobs should be like that too). There are already jobs with almost no positionals, to the point that ignoring them (or using True North) makes it irrelevant. We don't need to grind every job to mush to appease this hypothetical "beginner". The comparison with long cast bars is once again relevant- should we delete them from PCT or BLM because this "beginner" has never dealt with them coming from another job? Absolutely not. Same argument here.