No, what was staggeringly misleading is the amount of healing that healers had to do in relation to their GCD is much higher in the past than it is currently.
In the past, tanks did not have that much self-sustain nor mitigation. Tanks still had parry/block/blind (flash) as ways to mitigate damage. They had to "cross-class" skills like Reprisal and Rampart for mitigation because Rampart was a Paladin skill and Reprisal was a Dark Knight skill. Even so, the amount of sustain at their disposal was much worse than it is today.
Healers had less skills that were on the off-global cooldown (abilities) that healed themselves, thus -- more of their GCD used Cure/Cure II/Regen/Medica II/Succor/Adloquium/etc. This is largely more visible in Lv 50 Coils.
This is also due to the fact that healing in the past actually had more variance -- enemies can critical hit much more often, making healers actually heal more using their GCD spells.
As a result, the effect of using their main attack skill is much less noticeable. Especially if you include having multiple DoT skills to juggle around with different timers as well.
This means for each GCD skill, the ratio of the GCD spent on healing to DPSing is much more balanced in the past than it is currently. You would be spending more GCDs to heal than GCDs to do damage because you didn't have that many oGCD skills to heal. Instead, we had skills that improved GCD healing instead (Divine Seal, old Celestial Opposition + Time Dilation extending Aspected Helios/Aspected Benefic buff). We even had skills to REDUCE aggro on healing because healing too much was an actual problem (Ex: Shroud of Saints / Luminiferous Aether).
Now, tanks have been homogenized and gained a lot more % mitigation skills, especially once we enter Shadowbringers (a huge homogenization across the board for all roles). Tanks have also gained a lot more self sustain in Endwalker - to the point where they can keep themselves alive without a healer. Healers have such a huge abundance of healing power with healing abilities that majority of the time, they can keep up their single attack skill in each GCD and weave in a healing ability between GCDs instead. As a result, there is a huge imbalance between each GCD for the ratio of healing to DPSing. All the healing was just moved over from GCD skills to oGCD abilities.
However, the damage requirements never went up to account for this -- and by damage requirements, I am referring to unavoidable damage. Damage that must be healed through. Instead, they went down. Auto attacks no longer critical hits. There is much less variance to healing. There is MORE of a demand to mitigate properly - but this is also a party-wide thing if raidwides are lethal. It's not a healer thing when everyone is contributing to mitigation effort (Addle/Feint/Reprisal/Heart of Light/Passage of Arms/Troubadour/Shield Samba/Tactician to name a few).
Mechanics are fine, BUT they generally force healers to either "heal nothing because the party knows how to handle it" or "heal/revive because the mechanic is the type that one-shot a party member".
That inherently means the healer's healing toolkit is entirely dependent on whether the team is playing badly or not playing badly. If the party is playing fine, then healers do NOTHING BUT DPS because of the amount of time it takes for mechanics to resolve is much larger than actual unavoidable damage.
We don't use our GCD to set up stuff like Protect or Stoneskin anymore. We only really use our GCD for damage now. Except instead of having a variety of ways DPS like Aero, Aero II, Aero III, Bio, Miasma, Shadowflare, etc. all healers have is 2 buttons for DPS for most of the fight.
And healers have been consistently told that the developers will never increase damage to the point where we need to consistently heal. So, we're left in a state where healers have been using the same GCD attack skill (Glare/Broil/Malefic/Dosis) as much as tanks auto attacks these days.