Amazing, but with a somewhat expected simpler story line Whoever deluded h**self that any subsequent movie could surprise h** as much as the first one, is in for another surprise. That's not to say that the movie is not exceedingly and jawdroppingly enjoyable, just don't go in expecting to be re-introduced to this universe, that's all said and done in the first one.
This is your second tour to the planet, so treat it as such. This is the after. What else could you expect other than "life goes on".
Storywise, yes, it is a bit weaker, and the family "good" trope is really the only thing that bothered me throughout, both in the context that the Navi tribes do not operate in such a tight familial manner, and of course by my cynical view on the holiness of families.
In any case, go see it, if anything, it is money well spent.