The more I've thought about it ever since the run-up to Shadowbringers launch I've just felt like SE straight up doesn't find healers sexy in a marketable sense - people wanna play the cool Gunblade, your average player wants to play as a DPS and just hit buttons to watch cool shit happen, so Tanks and DPS get all this attention that healers straight up never get despite an entire expansion in Stormblood of Yoshi straight up saying the exact same shit he did when Shadowbringers was coming out as to why they couldn't do another healer yet, because it was too hard and they don't have a clue what to do with them, basically. Healers have a boring playstyle for the most part but the larger problem is that they just don't have a vision for what they want that role to be like and they don't care enough to put real hard dev time on re-working it like they do with the other roles which are just so much more marketable to do.
That, and there's the problem of the almost impossible fine-tuning to overall difficulty of the game. They want healers to heal more, but don't want to make the game harder to force players to heal more because, well, a ton of people playing this game are bad at it and wouldn't enjoy that either, so they just went down a checklist with Shadowbringers bosses of "well every single one of them needs a big AoE thing, maybe some more DoTs, cut down the timers on the regen abilities so we force players to cast them more often," etc, which didn't really accomplish anything except give healers busywork to sort of fake the fact that there's no real meat there.
The reason that a lot of people who play White Mage never really noticed anything about this was that White Mage is actually the only healer with at least a semi-formed interesting gameplay loop that combines both healing and damage, and feels kind of smooth to play, as opposed to Scholar and Astrologian which are just the clunk kings. That, and they lost almost nothing as opposed to Scholar and Astrologian which had so much taken away from them. The way the lilies work is actually kind of great, you use healing abilities and for that you get real meaningful damage. Astrologian meanwhile received a Heavensward-Bard-like gutting of anything that made it interesting and Scholar is just a mess with abilities that just conflict with each other - though it's an incredibly good healer, mind.
Like, the bottom line is that two expansions in a row of no healers kind of just reveals either how little they care about the role because it doesn't play well in advertising or just they genuinely don't know what to do with them - and it's probably just a mix of both. It's kind of hilarious to me that they did exactly the same shit with Scholar twice in a row with Stormblood and Shadowbringers - cut out the way it plays without any good sense of how it would feel to play it, and then caved after the expansion and gave an ability or two back and said "yeah I guess this shit is hard we'll get back to this in a year and ahalf because we apparently have more important things to focus on than one of the three main roles in the game." Better to rebalance Blue Mage like twice I guess.
I think ultimately what made it so painful for healer mains this time around is that Yoshi finally caved to the tanks that just wanted to be blue DPS. After years of fighting tanks who did everything they could to make the tanking aspect of the job secondary, and to finally get more people playing the role, he just threw his arms up in the air and said "okay fine, TP is gone now, aggro is practically automatic, there's no stance dancing anymore, here, just do whatever you want." But with healers we still can't get some sort of basic DPS loop that is fun at all because that's not whatever their screwed up "vision" is that no one can figure out anyway.