Can I give the movie zero stars? It deserves 0 stars.
TL:DR: This movie takes the adage "Show, don't tell" at face value and believes no effort should be made to tell you about what it shows you.
Go watch Edge of Tomorrow.
This review will contain spoilers.
1) Time travel, but how? The movie makes no attempt to describe how this technology is possible. Just that it is and makes use of hardware in the clumsiest way possible. Armbands? Really? And if you lose your arm which is shown to have an extremely high likelihood of happening? Why not neck collars? If you lose your head and it falls off, it's pretty guaranteed you wouldn't need the tech, but the guy that loses an arm is just left for dead even though he could have a chance at coming back without the arm. Sloppy.
2) They are in the future tech, but displayed genome sequencing at more or less thousands of times slower than what we can do today in the modern world. Travel to the future but bring your computer with you cuz they opted to Pentium Dual-Core e2000 to sequence the genome of aliens.
3) Why the family story? Seems awkward and misplaced. 500,000 people left on the planet, and one of them just so happens to be MC's daughter? This is more farfetched than the time travel. Guess they needed something else in the story besides expending munitions.
4) The aliens were basic predators. They pretty much had no advantages over humans. I can't see us not winning a war with these things purely based on attrition. The aliens from A Quiet Place? Yeah, we screwed against those armored tanks that travel on land at a pace of 100 mph. These chumps? They basically are mindless predators. I see no reasons why we wouldn't have won against the aliens shown in The Tomorrow War.
5) Lastly, why kick a dying creature off a cliff? Do you know how it reproduces? Do you know that the toxin is going to kill off an egg inside her? What if the splat at the end gave just enough wiggle room for an amniotic sac to just roll off into the snow to hatch another of these things. This is just me thinking of being overly precautious maybe, but I would've wanted to see that thing dissolve in front of me so I could search it's remains for anything potential survival of an offspring beyond the toxin.
This movie tried it's best, and it was a D-. It passes for entertainment, but only by the lowest standards.