Issue is, they used to be as fun/more fun that DPS by having skillsets for DPS making them two in one. The whole meme of DPS but blue and DPS but green came about for a reason.
But as the game garnered more popularity, popular opinion started to see a ton of folks who call a whambulance every time they have to do a modicum of effort to screech to the high heavens, "Waah! I don't like it being this way!"
This started mainly when the devs, in their infinite wisdom, decided to listen to feedback about Cross Class skills. There was out cry since ARR that Cross Class skills didn't have enough variety to truly be useful and that players just stuck with the raid optimal set all of the time, so we should just be given set skills and have these done away with. Wish granted! Monkey's paw curls.
The Monkey's Paw curling being that when they added role actions in Stormblood, they hilariously actually confused players responsibility. This has more to do with the new role actions that came about than the premise, but when you're designing "new" skills, you do actually have to bring something new to the table, and so they did. They did by giving every DPS an enmity reducing skill. They did by giving tanks a tank swap easing skill.
They did this, because they kept listening to player feedback of, "Tanking is so hard!" without actually delving into why they were getting that feedback. Reason they got and still get that feedback is a facet of player psychology. It's the mere addition of an added responsibility that makes people say that, not the actual game mechanics.
So what rippled on to occur was that tanks started to complain about enmity combos, something that had been standard in their skillset since 2.0. The meta in Stormblood became to have the entire party focus on enmity management so that tanks would ride DPS stances and optimally never come out of them unless absolutely necessary. This resulted in a lot of tanks becoming divas. Essentially making high end tanks actually demand to be worse at their role as a tank as an optimization for raid DPS.
They'd also taken this opportunity to radically alter Cleric's Stance down to a timed oGCD rather than an actual stance, a sign of things to come for healers. This change was met with cheers, the same as cross class elimination,, even though it made the ability almost functionally worthless, since its gain could go unnoticed due to crit/direct variance anyway (+5% damage for 15 seconds every 90 does not feel good or noticeable).
From these times they would get the feedback that healers needed to focus even less on DPS, that tanks hated their enmity combos not just in function but in appearance, and certain keystone skills in certain job rotations were used too much (See: Dark Arts).
So this rippled forward in SHB where Enmity combos were removed entirely. Goodbye some of the best animations for weaponskills of all time. Again, mindless change met with cheers by the masses. Cleric's Stance's vestigial form was also removed. Again cheered for. Protect was removed. Excuses made for. We start to see healers wake up en masse here, sort of the, "Oh no, we're headed down a bad way." Particularly noteworthy was the removal of Energy Drain from Scholar, which met similar backlash as the punishing Warrior gauge from StB. A change reverted by 5.1 or whatever, but merely a token as all other healer DPS complexity was steadily eroded.
Gunbreaker came out with its unique Continuation combo, while the other three tanks moved towards having an ability that set them up for a back to back resource free big hits. i.e. WAR clones. With no real differences in enmity building, this made the only differences between tanks become their ability to self sustain, their immunities, and their DPS output.
Not much changed moving into Endwalker. Every tank got a big hit stapled onto their rotation. Though PLD did get a fancy looking rotational shift with its giant energy sword magic.
Here in Endwalker though, we have seen the erosion even of DPS classes, so we're actually approaching the point where we're going to have to worry about whether they can make fun DPS classes or not. Instead of asking if an expansion could perform well without a new DPS, we should just be asking, "Can a new expansion perform well at all?" (or maybe, can they design any new classes well at all?)
And all these changes came from response to feedback. The feedback they responded to most was, "Here is stressful thing about Role X." So they removed the stress, thinking this would just make everything more fun. Thinking by removing stress they would make healing and tanking more approachable. But every time they removed something stressful, they also removed a small slice of fun. Until now we have almost no stress in our rotations, but also almost no fun.