That was fun! I haven't played many deck builder games. I only was able to spare the time to play a brief portion of the game so I didn't actually get to any of the actual deck building parts, lol. I had to call it after beating the first boss.
I felt the combat system was interesting enough to make this stand out from other RPG Maker games. I've not played very many of those either, but a few here and there. So the battle system is very appreciated. The animations all looked pretty good and the Quantum Star was appropriately very cool and satisfying to use.
The music selection was great as well.
I glanced through the other comments here and I have to agree that your idea to leverage the therapist session at the beginning to influence the starting deck is a great idea. It may also be a decent idea to give the player a few extra cards after the first battle as loot, but also to start that deck building part early as well.