Am I the only one that sees this as a Dark Comedy about CULTS?
I cannot believe all the posts saying this movie is bland, dumb, doesn't make sense, is not a comedy, is the ending fantasy etc.
A big clue is the name of the rebellious son - Raelian. This is a very weird cult indeed, somewhat like the Scientologists.
https://www.google.com/search?q=Ra%C3%ABlian+movement&pws=0&gl=us&gws_rd=cr
Maybe it's because I'm a quirky Brit but to me the entire movie is a Dark Comedy about cults, religion and extremist ideas.
I don't think you are meant to take everything literally as a believable story. The entire thing is deliberately 'over the top' and far fetched. The movie even makes fun of itself - eg. walk out of the diner because there is 'no real food on the menu' then next scene they are eating a huge chocolate cake and Ben is squirting artificial cream directly into his mouth! Hilarious!
The entire movie is making fun of a whole host of issues:
1 Parenting
2 Cults and Religion (see below)
3 Meat eating
4 Hunting
5 Rich vs Poor
6 Consumerism
7 Capitalism vs Socialism
8 Survivalist America (the end of times is coming, go live in the woods and prepare for the Apocalypse)
9 Guns/Weapon owning (and especially around children). But hey if the zombie apocalypse is coming, right on!
10 Fast food
11 Medicine/healthcare
12 Mental illness
13 Cremation versus Burial
14 Teenage rebellion
15 Elite Ivy League university education - who is it really for?
16 Hippy culture
17 Elite culture (the Bach references, the quantum physics references etc)
18 Conformity to societal norms (or not)
The list is almost endless. Like a fine wine, repeated viewings will surely highlight some more. I think this might be destined to become a cult classic.
On point 2:
For me the main takeaway was that almost all religions (or extreme ideological ways of forming a social group) start as a personality cult around a single person (or two) and their hardcore beliefs. You could argue that Ben was starting his own cult around his immediate family, and he probably didn't even realise it himself. His wife was supporting him in that endeavour.
His wife's suicide and her parents 'intervention' is basically the catalyst for preventing that and bringing them back to more mainstream living. If that had not happened the studio could have made an interesting sequel where the eldest son returns from his travels with a wife and they have kids and carry on the family tradition and 'grow the cult' even larger. That would be an interesting sequel...and maybe in Captain Fantastic 3 we have the survivalist-come-anti-religious version of the Westboro Baptist Church.