I would bump it to as high as a 6/10, if only because they answered the question that was pissing me off about the nature of the alien invaders since they were first encountered in the movie. Too many movies would have just left that hanging (even if they left the ultimate origin question hanging anyway, because it was outside the scope of the movie).Bleah. 3 out of 10.
I found it hard to believe that world governments would buy into the future war idea to institute a world-wide draft system. I found it harder to believe that once they did accept that, they would not follow up on the toxin at the end. Even without a connection to the future, manufacture and stockpile the toxin all over the planet, but especially in Russia.
Speaking of utilizing the tactical advantage of being in the past, I also found it very difficult to believe no one but Forester and his wife thought about trying to affect the war from the past, and figure out when/how the aliens arrived. Also, why did the future not send back reports of engagements with the spikes, with when and where they took place and how they turned out, with instructions to preserve them so humans in the future could review them and alter their plans accordingly. Maybe it would be too close to Tenet?
The aliens are basically animals. I don’t understand how they managed to build a spaceship (maybe I missed some exposition about somebody else sending them?) They also suffer from the Aliens/Ninja problem: one is basically invulnerable. But a hundred can be mowed down with ease.
There was exposition about how the aliens were actually cargo -- a biological weapon being delivered before the ship ran into trouble -- basically the screenwriter ripped off the ALIEN series.