To be fair this film could do with a sequal to get the writing down or just to go full insanity.
For example instead of fighting for future earth, they are now pulling people from all periods of earths history to fight the spikes on multiple different planets. Then it could turn out instead of these being the actual people with all the issues that entails they are just cloning people with good solider genes again and again to throw into the meatgrinder and the memories our characters have are the genetic memories of their progenitor DNA. Not going to win any awards but could be a good fun movie at least which is what they seem to be going for.