By far the deepest and most mature entry in the series, and my favourite. Being the first game I played as an adult, I definitely appreciated its depths. So many character arcs to bring to a close, and it nailed them. Gameplay had me WOOOing at so many points. It was so cool, after kh1 and 2 catering to classic disney movies when I was a kid, for KH3 to hone in on moderns like frozen and bh6 as an adult.
Quality was there, but quantiity was short, due to delays. The full game is 0.2 (the demo), base KH3, and KH3 REmind. I am confident when remind (ergo the whole game is released), it'll be the banger that these disappointed fans want.
I recommend waiting for REmind if you haven't got it already.