The only reason why healing is a mess is because of a diffirent issue.

If healers are more difficult, it generaly means players will be less healed up, and die more often. These deaths will be blamed on the healer (instead of the player standing in the AoE). Simply because players are realy bad at looking back in time, and looking at others (only healers do this well as thats their job). If healers get blamed all the time, it hurts their popularity even more. And this is what they want to avoid, so they actualy are too easy and effective.

As a result, healers got excessive healing, and a lot of classes got self heals to again mitigate healer mistakes. It just oversimplified the role.

But on a side note, i have noticed in plenty of cases where teams were new to a dungeon, that as healer you are getting pushed quite a lot already (and its generaly also the most fun as a healer with it). And to me that actualy shows that the kits of the classes arent actualy too bad either. Its just that most of the time you are simply not demanded to use this kit and can just resolve towards abilities that preserve most dps.