This is a beautiful movie with a nice cast that suffers some from the writing. I don't regret watching it but I do have to admit that some aspects of the plot just don't make sense. It could also be a drag if you dislike slower films. That all said, I think people are being a bit harsher than the movie deserves: not all of the plot holes are as bad or important as many reviews make out.
Major plot points (aka Spoilers):
Dying Earth: while it is never directly stated how or why it is dying, I think that doesn't matter. The important things are clear: something in the air is making people deathly sick, and whatever it is is spreading rapidly across the globe. It could be an airborne disease, a sudden pollution spike, radiation, etc. All that really matters is that the Aether research ship cannot land without dying, so Clooney has decided to use the last of his time to warn them and give them the option of returning to K23.
The Arctic: this is where things get a little more confusing. Clooney finds what appears to be an abandoned (and mute) child after we see everyone else haphazardly flee the arctic station. Presumably none of them are interested in living a little longer. The girl is found after nearly burning down the kitchen and Clooney takes her under his wing. He even goes to great lengths to keep her safe as they travel to a different station (which is for some reason necessary as it has a slightly larger antenna. It's unclear what the first station was for if he's an astronomer). Ultimately we find out that the girl doesn't exist, as she is a younger version of his real daughter who shares the same name and is on the Aether. I guess she was a hallucination caused by Clooney's unnamed terminal illness? But that doesn't explain the fire or why she seemed so real. Another seeming plot hole is Clooney's reliance on some sort of dialysis machine, which he loses at one point. Despite the emphasis placed on its importance he faces no issues greater than sweating and increased vomiting after losing it, meaning it was essentially a complete waste of screen time to watch him use it multiple times.
The Aether: probably my favorite part of the movie. The crew get along well and are calm and composed through multiple emergencies. One thing that makes no sense is the "unmapped portion of space" that they have to fly through after suddenly going massively off course for no reason. They are more than halfway back to Earth at that point, there shouldn't be multiple random invisible asteroid fields. It feels like it was forced for the character death and cinematics. One thing that I think other reviews have wrong is the very ending on the ship. Yes, it's true that the last surviving crew members can't feasibly Adam and Eve their new planet. However, I don't think that the movie in any way suggests such a happy ending. The ending feels tragic, not promising and hopeful. I believe the couple are well aware humanity will die with them. The point is that they will at least get to live out their lives (and their children's lives) if they can make it back to K23. It's better than nothing.