I know exactly why the critics bashed this movie. I'll tell you right now, it isn't a very good reason. I'll start off with that, the bad. The plot was a little generic. That's it, that's the reason this has a bad score on the ol' rotten tomatoes.
However, as generic as the plot might be, they managed to make it interesting. The combination between the CGI and the backstory of the characters made the movie just different enough to make it good.
I think it's worth seeing for the CGI and visuals alone. The movie was stunning to look at. I mean, massive cities on wheels roaming around a barren wasteland. Can't really go wrong there.
If you like dystopian style films, you'll enjoy this. Super fun to watch, recommended.