I recently came back after quitting due to ShB changes to my main class: Bard. This thread feels too similar and my heart goes out to all the AST mains angry by these changes. Even back in Stormblood (I regret that I didn't pick it up then), I enjoyed the cards and the various support they offered. The mini-game itself felt so different from the other healer mains too.
I picked it up for powering through ShB's main storyline and I do enjoy it more than I do SCH or WHM, so I'm very much a casual when it comes to this class.

For the DT changes, the one that baffles me most is the removal of RNG linked to the cards. I mean, you're playing a tarot deck so that makes no sense from both gameplay and identity perspectives. Why would the randomness be the issue with a class that...draws cards?

I unofficially main FSH, and I know its RNG. It can be my best friend and my most despised enemy (looking at you Ruby Dragon). RNG by itself is not a problem as long as the player has tools to direct a positive outcome or mitigate it. And from what I'm reading so far it seems like AST players did indeed have those tools readily available back in Heavendward and Stormblood. Heck I would even argue that RNG makes the class more resistant to staleness compared to others.

Adaptability. Isn't that what AST is supposed to be about? To adapt to the fight with the cards you get instead of focusing on 100% reliable pre-packaged "sets" of cards?

My question to the dev team is simple: "What do those changes do to make the class fun for new and veteran players alike, while keeping its gameplay identity/loop?".
The DT variation of AST doesn't look fun, so I don't think I'll even bother with it unless my FC needs a healer for normal content.