This is such a good post, OP. The summary is so accurate I could not have done it better.

Originally a WHM, I picked up AST after realizing how dumb the Lily system back in Stormblood. Leveled it to max, and have since been proud to call it a main. While I did consider expanding my healing career by trying SCH, I never went with it because I was perfectly content playing AST.

Then Shadowbringers came.
AST card changes and removal of time extend buffs has soured my excitement for the job. I still leveled it to 80 first. Forced myself to run instances with it for a while. But in the end I just couldn't go on. That was also before AST received plentiful of potency buff so I 'gladly' transition to WHM since it's the only other healing job I have. At least the Lily system works better this time, heh.

Now, after almost a year mourning over the state of healers, I decided to pick up SCH. I switch between SCH and SMN during the leveling process and boy... I regret not picking the job before it gets butchered in ShB. I have come across SCH posts many times in healer threads about how previously they would need to manage dots, have 2 fairies with different functions, etc. I could only guess how it feels through playing SMN but still, it was so unfortunate that I missed those good stuff in SCH.

SE wants healers to do more healing? Well, even while leveling SCH I still use most of my aetherflow for ED rather than healing even accounting Art of War spam.
Also, AoW during trash makes me feel like a WHM wannabe and it doesn't even have CC to be using it upclose. -_-