Biggest problem: storytelling and budget
After watching this movie, I totally agree with the average overall score of ~3.
The reason is that the entire movie tries to play on a very gigantic catastrophy - an alien invasion, yet in total, you see about 5 or 6 people in the film. Supposedly there is a Mars colony with hundreds of thousands of survivors and a lot of survivers on earth too, yet the defense of an entire country falls on three people in mech suits. It just feels cheap that they didn't have a single stand in soldier or civilian.
I think mainly this was a budget restriction, but it really hurts the movie.