>>51216536Think of why RPGs are enjoyable in the first place. Some will stay story, but I'm talking about the mechanical aspects of them, the hooks that get in your brain.
Leveling up a team of characters, making them stronger, customizing your team, picking the right class combinations and equipment, conquering increasingly tougher challenges.
Now think of an RPG except your team of characters has to be assembled from hundreds of different "classes" all with their unique characteristics, both gameplay-wise and in terms of design and personality.
Add a premise of starting out of nothing as a 10 year old kid and rising to the top as a champion with your personal team of creatures, and if you don't get why it's appealing yet then I can't help you. The level of player expression is a big deal and not present in any other big RPG franchise, not like this. Your team will feel like your own, and that also leads to replayability as well.
