If you are going to suspend your disbelief, then I guess you might still get a little entertainment from this movie. A great line-up of actors, nice cinematography, so-so cgi effects, and an intriguing premise.
Personally, I didn't like the movie. Its nice technical aspects were drowned by its plot full of holes. I had a lot of questions, and when answered, the movie wouldn't technically exist. One example would be, why build a train? It's a moving engine, and just like any vehicle, it would need something to power it up. Where do they get the resources, especially in such unfavorable conditions? Another would be, why take in poor people, and accuse them of freeloading? They could've just left them to die outside. It would've been more logical if those poor people were took in to work for the rich, but in the movie so far, they're doing nothing (except for the protein jelly cook, violinist, and 2 machine workers), literally freeloading, and an absolute waste of resources. The only reason why the movie exists was because of the cliche classism.
I also found it hard to sympathize with the main character. He had no personality, and he didn't know what to do after the revolution. That's not how you stage a coup d'etat.
Finally, the ending's a mess. Blowing up the train and everyone in it, throwing away what little resources you have, just to go outside. 2 kids were left, like there's hope left for humanity. Unfortunately, interbreeding is not good in propagating a dying species. And also, the polar bear didn't make sense. If all living things had gone extinct, you wouldn't expect to see life in like millions of years.