They cant change it because the "i dont wanna DPS as healer" crowd would go mad for STILL having to push non-healing buttons, the "I want to look cool in the logs" crowd will go insane because they suddenly have to fix mistakes of other players to a larger extent, and the playerbase as a whole, used to a very simplistic playstyle, would just quietly quit over the increased difficulty of encounters.
You have to realize, the silent majority just leaves games, sometimes suddenly, and has them die. Happens all the time, and if it happens here, I dont think SE will give the game a chance to recover instead of just dumping it. Shadowbringers post-launch is proof that there are minimal ressources invested in comparison to earlier in the games lifecycle, we are nearing the end. A re-design that increases complexity is the opposite of what mainstream game design dictates.