Healing is not hard

[Absurdity]

I would disagree. Even in other MMOs with simple healing spells (e.g., Vanilla WoW), the challenge was in the triage and resource management, without skills being whiz-bang intricate game design capstones. Do you risk a slower, more efficient heal or drop your fast inefficient heal to avoid a tank staying in the death zone? Is your MP consumption sustainable? Are you standing in the optimal place for AoE heals to be effective? How long can you save your emergency cooldowns, in case there is an error? Some of the "simple heals, high skill ceiling" concepts like cancel-casting big slow heals isn't really feasible with FFXIV's engine and game design, but you absolutely will be stimulated if enough incoming damage hits to where healing requires strategic choices.

I agree that FFXIV throws too many tools at healers, and some of these options should be swapped out for mitigation cooldowns. But don't knock triage without trying it.

Ask any Holy Priest that played back in vanilla WoW and they would probably tell you that healing back then was incredibly boring. It consistented mainly of pressing a low rank single target heal every few seconds (or cancelling it halfway because it was no longer necessary) and then standing around doing nothing to let your mana regen. There was very little to consider because if you needed to start spamming Flash Heal it was a matter of seconds before you ran out of mana.
Was there a big emphasis on resource management? Sure, but if it means simply not doing anything I would not consider that an improvement.

Not a great example for good healer gameplay.

Although I'm sure a lot of the "healers are only there to heal" players are the exact kind of people who loved healing in 2004 WoW, since it meant doing nothing for long stretches of time in a fight, the same mindset they now bring into XIV and sandbag every Duty Finder group.

I've already seen a lot of complaining about how 'mages shouldn't heal this is dumb' but I wonder how it'll go in practice, maybe once people can actually play it they'll come round to it, or maybe they'll say that the 'spirit of vanilla is dead' (as if it wasn't dead already)

I'm not surprised, because while healing in vanilla was incredibly bland it came with one important thing, power.
Healers were always needed but, just like in XIV, barely anyone wanted to play them. So the people who mained a healer had a significant amount of pull since if they left the raid would simply grind to a halt.
Mages, or really any dps, being able to heal encroaches on their territory and how dare this dps class with proper gameplay outside of spamming Lesser Heal rank 3 try to take MY job?