I once had a RDM who did nothing but their Black magic abilities and never meleed. We should reduce RDM's abilities to 3 buttons (melee, short cast, long cast) to make sure all RDMs balance their magic. Actually reduce it to two buttons to lock them into using their melee attacks. See how bad that sounds? This is the reasoning you're using if it's just about healers incapable/refusing to heal. Regardless of how unbelievable brain-numbingly simple you make a job, there will always be someone who finds a way to play it poorly. We should instead focus on bringing up complexity in optimal play... Easy to enter, very difficult to master is what ALL jobs should be striving towards.
And we've been complaining about this (both tanks and healers) since ShB was released. We don't want to just be punching bags and heal bots. We want complexity too. Hell, it doesn't even have to be complexity in their DPS rotation, but unfortunately, due to the fight design being the same every time (i.e. we learn the fight thus know exactly when damage is coming) it ends up being the only thing that can be complex (in the end, DPS is the only thing that matters. A dead boss = the ultimate heal). We want each job in a role to be different and to allow us to grow and excel at these jobs. Plus having very different ways to get the problem presented to us done is fun.
(pure speculation time) It's actually quite possible they did. There's only 4 people on the job design team. So making all the healers/tanks the same makes balancing them much easier. I think they aimed for balance over everything this expansion and it resulted in homogenization to the detriment of diversity and (IMO) fun.
This is true... In ARR. Everything beyond that they 100% include healer DPS as it's pretty much impossible to meet enrage without healers doing DPS. Cleric stance was removed in Stormblood (or change to such a huge degree that it became a small DPS buff window instead of a massive "stance dance" ability). DPS reduction was done an expansion later in Shadowbringers.
Nobody wants them to die to do damage, but that's not the jobs fault... That's the person playing the jobs fault. Don't blame the tools, blame the craftsman.