The movie is all about subtext.
There's a really blatant subtext: about guys blowing shit up, exploiting women, and in general driving the world into total destruction. On its face, it's an exercise in radical feminism.
Except, it isn't. Below that, there is the layer showing that women are equally capable of destruction, and that they in fact need to rely on that destruction to reach "the green place".
And that's flipped on its head again, because that war machine runs on a mixture of fuel and mother's milk. Max is pretty much annointed with it when he uses mother's milk to wash the blood of his face, after a selfless act. There's a huge "war turned into a nurturing thing" there. It's echoed by the fact that part of Furiosa's body is partially mechanized. (Her replacement arm)
Which leads up to what I think is the final message, where the realization strikes that there is no separate, women-only feminist utopia. There is no "women peaceful, men violent" dichotomy. Instead, the world is finally improved by the women reintegrating themselves into the world they left, but on their own terms.
It's pretty much a post-modernist deconstruction of war movies and feminism at the same time. It's incredibly heavy-handed about it - all those things have about the subtlety of a hand grenade as a can opener - but it tackled a topic that was important and little talked about.
That is why it was a good movie. If that message doesn't speak to you, I'm not surprised you didn't like it. You were not the target audience. (Neither were people who like chase-and-blow-stuff-up movies, and they were vocal about the fact they didn't like it)
That doesn't necessarily make it a good movie, but if one liked both the subtext and blowing things up, they had a great time watching it.