There's a delicate balance between 'too much effort for same output as alternatives in the role' and 'not engaging enough'. If we took, for example, MCH's hypercharge windows, remove them, redistribute the potency into stuff like Air Anchor or Drill, it'd do the same damage, but it'd feel so much emptier, because it no longer has that frantic 1.5s weave-mash section of it's rotation. The same could be said of DRK, not so much anymore cos of all the extra OGCDs they've crammed onto it, but when the rework first hit, it went from busy, hectic, constant 'try to have mana for trick, but dont overcap' management, with a 10% haste effect on BW to make it even more frantic, to WAR speed. And WAR's slow, very slow, FC hits hard, sure, but Upheaval and Onslaught don't exactly make it 'fast paced', especially back in SHB when the CD on IR was 90s.
Some people like to play the fast stuff, for whatever reason. I wish we had a 'fast healer' option, for those that want it. SGE could be it, with some tweaks to OGCD effects, but SE seems content to have SCH 2.
Bit of a false equivalence there. And Clemency's a bad choice cos it's a GCD and we hate those. If they were given 'AOE Clemency, costs Oath Gauge and is OGCD', people would absolutely use it. Your example would be closer if it were more like saying 'Tanks were given selfhealing tools that are so strong they can do EX roulettes without a healer. But they shouldn't use those tools, because healing is not their role'. Whether you like it or not, there's overlap between the three points of the trinity. DPS have some selfhealing (in the case of SMN and DNC, party healing too) and self-mitigation to stay alive, like Radiant Shield and Shade Shift. Tanks have more and more DPS tools added, like Blades combo, Primal Rend, Shadowbringer and DoubleDepression (it didn't crit), alongside crazy amounts of selfhealing added this expansion (Holy Spirit/Confiteor/Blades now all selfheal, Bloodwhetting is Bloodwhetting but Nascent in SHB was already out of control, Heart of Corundum's Excog effect and 2 Auroras, only DRK is kinda left out of the party, presumably due to TBN's 'effective healing'). Healers, likewise, have some ways to mitigate damage like Exaltation or Aquaveil, mostly used on Tanks but can be used on others for, eg, soaking a tower, and yes, they do damage. The issue is, the way they do damage keeps getting reduced, because people complain they 'picked healer to heal'.
If you've been playing since 2.3, you'll know that since 2.3 Healers have been trying to push damage more and more. This isn't some new trend, and it's not unique to FFXIV either. Most games where there's a Healer or Support role, the Healer or Support is actively helping in whatever way they can, and 'do damage' is ALWAYS a viable choice on what to do next. Harass the enemy laner in League or DOTA, help shoot and down enemies in FPS games like Apex, help damage enemies(when your team's not going to die cos you stopped healing them) in Overwatch, do damage to mobs to clear the M+ dungeon faster in WOW. If people 'play healer because they don't want to do damage rotations', they'd better play a game that hasn't been forcing (via enrage timers) healers to do damage for the better part of 9 years, eh? Though, with how, as previously described, most games expect healers to do something beyond 'sit there with their fingers up their backside waiting for damage to heal', they might be looking for a while