As tiring as it is, it's still best to dismantle the "roll a DPS" argument than to dismiss it. Not for the sake of the person making that argument, they've already made up their mind, but for the off-chance of someone else reading through and needs convincing that we need to be more than healbots. Even with the 100 pages of debate that would convince most reasonable people, someone new jumping into the discussion shouldn't have to read through all of that when it's easy enough to repeat the counterpoint anyway.
If tanks can get a healthy mix of damage buttons and mitigation buttons, then healers can also have a healthy mix of damage buttons and healing buttons. If DPS can get the occasional mitigation or healing utility outside of their role, then tanks and healers should also be able to do things outside of their usual role.
This goes back to a larger point that Square really needs to learn at some point; we're not simply playing a role, we're playing jobs. WHM should feel like a master of the natural elements, wielder of holy magic, capable of sanctifying their teammates and smiting with righteous judgement. Instead we stare menacingly at the opponent for 30s straight and pop a flower every now and then. AST should feel like a manipulator of time and fate, capable of bringing good fortune and reversing/accelerating pain. It has some of that fantasy within the healing kit, but not in the barebones Malefic spam, and the duplicate effects of the cards don't make me feel like I'm doing anything with fate whatsoever.
Relegating healers to only healing is also counter to how the game has been designed for the past 11 years. It would be a massive time-sink to redesign all that content to make us spend most of our time healing, and would massively increase the skill floor, effectively only keeping veteran healers around. Whether we like it or not, content has to have some leeway on the amount of damage it can throw at us (even if I agree that it should be less lenient than it is now) purely to let less skilled healers catch up with healing demands, as well as to let the team overall make a few mistakes without causing wipes. The moment you have that leeway, you also make room for damage, and that should also be more engaging for healers than a nuke and dot.