The biggest thing to me is that, unless running an all-physical party as of Shadowbringers and thus having essentially infinite AoE, you simply cannot sustain an AoE in many a full pull without healer DPS or badly outgearing the instance; there's just not enough MP (or, formerly, TP).
That would be because heals-only healers are very different from those who
The latter are literally cannot be called "heals-only healers" because they clearly do not solely heal.
The reason for anger, too, is obvious; no one playing a toolkit to its full potential, or attempting to do so, likes hearing that what you do is impossible or out of scope by principle of some mistakenly rigid belief as to what your role entails. It's like being told to be intentionally useless and unambitious, despite having all you need to be of value right there at your disposal.
The advice, then, for such mistaken role definitions: Jobs make clears. Best use of jobs makes best chance and speed of clears. All else is irrelevant. Making our HP not hit zero (outside of sacrifices which increase the chance and/or speed of clears) is a thing everyone does. Making enemy HP reach zero is a thing everyone does. There are no unique tasks in this, only best fit optimizations at a given point in time with future events (potencies, duplication, and modifiers) in mind. No task or responsibility ends for one "role" where another "role" begins. Don't worry so much about what is and is not your duty or fault, but rather merely what is wasteful and all that is not. Or, more simply -- Just. Play. Well.
This is all good and well but ultimately will not change the outcome of "heal-only" play unless healers are wholly reduced by damage intake to heal-bots, which I doubt would create any more compelling of play.
I'd like to see healing take up the majority of my time as it might have at minimum ilvl situations back in certain pre-nerf ARR dungeons. That does not mean I want to just be spamming heals under the threat that if the tank isn't topped off the next cast-less special attack may wipe them out. That does not mean I want such sustained damage that my only option is to chain Cures with a Cure II only being spliced in to recover from casting Regen. And, so long as that's the case, you're still going to have this principle split between those who refuse to understand gameplay from beyond solely a healer-centric point of view ("I can just... heal more, no matter what happens to tank and DPS CDs or that 50% haste buff those mobs cast after 40 seconds...") [heal-only healers] and those who are willing to know exactly what their toolkit can do or best fit a given situation [everyone else]. So, no, the point is not outright missed; the changes just aren't likely enough to circumvent the current "tip-of-the-iceberg" issue, either.