Listen, it's a tech-demo. This was released to show what kingdom hearts was going to look like on the new generation of hardware, and they definitely had some growing pains to go through using unreal engine 4. As your game gets more realistic, the 2d characters get more uncanny, and it's tough to find that middle ground (see "jump force" for reference).
That being said, it still feels like classic kingdom hearts. the combat doesn't feel as smooth as kh2, but it's nice to move away from card battlers after doing so many in a row. Also felt like Nomura just had a couple things he wanted to figure out how to explain before the first game to try and tie things together. did it work? That's up to you to decide for yourself.
I beat it in just over 3 hours so it's incredibly short just fair warning. The music though, is just exceptional