Isn't this true of all content, though?
Not everyone who does Ultimates, Savages, Extremes, Criterion, etc enjoys it. Not everyone that plays X Job (fill in X with literally any Job in the game) enjoys it.
Unless you have a scientific, official poll of people to determine how many people play a Job and enjoy it vs those that play the Job and don't enjoy it, this is a meaningless argument since it applies to literally everything. "People like BLM because it's a challenge! This proves people want Jobs to be more challenging!" "Well, not everyone that plays BLM enjoys it, just like how not everyone who did Eureka enjoyed it."
Would you accept that as a valid counter argument?
You could try to move the goalpost "SURELY no one plays BLM unless they enjoy it! It's not like it does more damage, can be a ranged Melee, or has any advantage or benefit where anyone would pick it over an easier Job!" isn't really a valid argument, either because (as I sarcastically stated in that imaginary quote) there are advantages BLM holds over SMN and RDM that might make people feel pressured to play it even if they don't really personally enjoy it or what it requires of them.
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So you can't really use this as an argument. ESPECIALLY since it's not in vacuum:
WAR is one of the top played Tanks (even before it became top damage, it was still highly played)
WHM is the most played Healer (despite it being the least meta choice and weakest overall)
DNC is the most played Ranged (this also destroys the argument WAR and WHM are only most played because they start at level 1, as DNC clearly does not)
SGE is the second most played Healer and is the second easiest and easier than its competition, SGE (again debunking the "starts at level 1" argument)
RPR is the most played Melee outside of JP (and 2nd there) and SAM the most played in Japan (2nd in the West), and they are the two easiest of the Melees to play to most people (again debunking the "starts at level 1" argument)
The people kind of have spoken.
My personal philosophy is the game should have a range of Jobs from simple to complex (but you know and disagree with this), but the alternative is them all being WAR/WHM/DNC/SMN-like. I just think they need to stop changing existing Jobs. Adding new Jobs for new playstyles is the way to go. If they want "simple BLM" in the future, they need to leave BLM alone and just add a new Caster "elementalist" or whatever to fill that niche. Don't take from people what they already have, that's my view. And this goes both for making Jobs simpler and for making them more complex than they currently are.