The latest demo is pretty concerning from a gameplay perspective.
Battle systems are basically the bread-and-butter of RPG gameplay, and from what we've seen in the Platinum Demo's adult Noctis segment, what they've landed on isn't particularly good or engaging - and even more disappointing if you've come to expect good things on Square Enix's action-RPG front from playing Kingdom Hearts. I know their intention isn't to emphasize the action aspect, but that doesn't change the fact that the system they decided to use is based around it.
There's little more to it than "hold B to attack" and "hold X to not die (most of the time)," which isn't do much for instilling hope in the system's potential. It's entirely possible that this could be the most basic combat possible, and that additional skills, abilities and actions are unlocked over the course of the game that make things far more interesting and interactive... And I certainly hope that's the case.
If you have an Xbox One or PlayStation 4, go download the Platinum Demo and give it a playthrough. You might feel differently about it, but it's enough to make me consider not purchasing a mainline Final Fantasy on day one.