I could never make it through Star Wars so many years ago because I also found it so moronic but in that dreadfully smug Hollywood kind of way. It had a kind of antiseptic chilliness about it which never touched me.
Too very slick like so much from Hollywood. And yet, I know that the story was supposed to be one of heroic Greek stuff lauded by the great Joseph Campbell, but, non! non! de tout!
Now, John Carter does not pretend to be a anything but a romp; a weird campy lark between comic book pages so unabashedly stolen from another era completely. The story is so wacky that it actually works. It manages to pass through unscathed, that delicate and surreal zone which can make or brake our tolerance in Sci-Fi. I found myself completely unhinged from reality after just 10 minutes into it. Embracing its abstraction it stays true to its B-movie integrity. I think what really saves it from many possible disasters is that the main characters play it cool and, they have a certain likable charisma, not a wink, but a subtle smile to the audience (and each other) as if to say: "Isn't this pretty wild and crazy?" without an cheekiness visible.
So, my advice is to watch it with the kids, or just alone, with a large bowl of chocolate ice cream, fudge, and sprinkles on top.