I don't even know why "pro-healing" vs "pro-dpsing" is even a thing when they're both two sides of the coin that you have to balance.
You don't get to just heal and only heal anymore, and you actually have to interrupt your dps in order to heal at times. That's just how the role works.

Even in old "classic" MMOs, healers wouldn't be healing all the time either. They just stare at the screen for 30 seconds, and just afk until someone takes damage, and then they heal back up.
Healing right now is basically the same thing, except instead of actually afking, you actually play the game and contribute to the team by doing the only you thing you can do, dps.

Literally the only difference is if you should dps within that downtime where people aren't taking damage. That's it. That's literally what most "heal only" healers are complaining about.
"HOW DARE THEY ASK ME TO PLAY THE VIDEO GAME INSTEAD OF SPAMMING CURE 1 HURR DURR"

Even if Square Enix adds actual unpredictable damage to content, people are still gonna dps, because there's going to be windows of opportunity where everyone's topped, and there's 5 seconds before the next damage instance will come out, and that's an extra dps spell. You will never eliminate dpsing from the role because dps IS downtime.

Even WoW, with lower healing potencies, lower healer damage potencies, a lot less mitigation for tanks in general, and a lot more outgoing damage in raids and Mythic +, I still dps as a healer, because there is still downtime in content. There will always be downtime in content. Hell, one of the healers actually need to dps to heal everyone back up (Disc Priest).

So why not make give healers that WANT to make that downtime interesting, the tools to make it interesting?
Giving healers more dps buttons to push isn't going to harm you folks who like staring at hp bars and casting a heal every 15 seconds. It's not gonna lower the skill floor at all. Healing will still be the accessible, easy role it is right now, and the casual content is still not gonna have tight dps checks, so you guys won't be affected by the extra dps buttons. Feel free to press Cure 1 to your heart's content.

What it will do is raise the skill ceiling, give the healers more room for skill expression and that's what's sorely needed in the game right now.

For people like us, healing someone is just the base thing you do, just like dribbling in basketball.
I understand that for newer healers that healing a tank wall to wall is satisfying, the same way you first learned how to dribble the ball on the court.

But we need room for us to express our creativity in dribbling the ball. In shooting the ball. In carrying the ball and passing the ball. In defending the ball.
More dps options will give healers that needed factor in the job design, one that's sorely needed for almost every role in the game right now.

Us breaking ankles on the court is not gonna affect you people who like to only dribble. Have fun with dribbling! That's okay! You're not going to be forced to do more than dribble the ball if that's where your satisfaction lies. You shouldn't be!
But don't stop us from trying to do tricks on the court, cause that's our fun. Us doing these tricks won't stop you from just dribbling the ball, so don't stop ours.