You can go on YouTube right now and find a thousand videos of healers in casual content back in ARR, HW or even Stormblood ignoring their "extra" DPS buttons. In fact, a lot of them would just stand around doing literally nothing at all when they weren't using GCD heals like Physick, Cure, Adlo, etc and content was cleared just fine. We can go back to how the game was before and the world won't end, nor will the vast amount of healers be pissed off.
The large majority of people who play the game will never play any job optimally in casual content, and that's OK. There's a reason the casual content is designed for all levels of skill in mind. Changing job design to accommodate these people does nothing but hurt the longevity, replayability and the desire to improve as a player. Unfortunately for SE, there's no amount of healing difficulty increases they can do that will make Glare/Broil spamming fun... so the easiest conclusion is to make the DPS kits have a bit more depth. The biggest failing of the healer role is that all 4 healers play like this and having no escape for anyone who doesn't find it fun.