There are parts of the story and maps we simply can't get to because they aren't there yet (I imagine about 30 to 50%), and there's a limit to how much we can improve our relationship with the various characters (which means that there's probably a significant amount of voice acting we can't hear yet), all of this clearly indicated as provisionally cut content ("you might be able to do this in the future", "can't go there yet", "what happened after this is, for now, literally indescribable", that kind of thing).

There's also what's clearly provisional concept art from time to time, and plenty of placeholder character models and art (plus keepsakes, and fish, the later even having generic descriptions), and there's almost certainly missing gods and characters (though there's no indication of which those might be and in which number).

So, yeah, it's not complete, by a long shot.

That said, I'm fairly certain that there's already as much content and story as in the complete first game, if not more, or at least it feels like it. And it's just as fun.