I'm quite shocked by the number of 5 star reviews on this. Typically in an abstract movie, there should be a resolution or eventual explanation or clear meaning to all the questions each event brings up. In the case of Heron, there are about 3 new questions brought up per scene and at most 1 is ever answered. The movie is overall very confusing / challenging to watch because I have all these loose ends I'm trying to seek answers to from before and instead I'm just handed more things to be confused by.
While I do see the metaphors for grief and balance in life / world which are disturbed by arrogance, it's just all too jarring to enjoy and there are too many things left unexplained but with a rushed pacing that seems to assume it all makes sense.
I agree with others who recommend to not watch this if you are a Ghibli fan and want to remain one.
The closest comparison I can make is to Spirited Away which is also quite abstract but at least in that movie the pacing there feels right and you feel emotionally in sync with the character. In spirited away I am able to emphasize with evry character I encounter and their actions all make sense given their motivations and knowledge I know each one has. In this movie you don't really feel much for any of the characters because they do things which don't quite make sense given their background and not enough time is spent with the new mom and perhaps not enough of the main character's inner emotional turmoil about his situation shown to connect with either of them. Just not enough investment in the characters to justify a lot of what they do.
Overall the movie feels half baked.
It could use a longer run time, more tie ins for the loose ends, and the movie lacks a signature musical theme which most of the other Ghibli movies have.