I really liked the idea of people from the future entreating their ancestors for help. This is something that really resonates within the Black community, and one of the ways the movie could have made itself more interesting was by having the Black side character, who believes he is a coward, the lead character of the movie. That way we would be introduced to a person who is not brave, and has been drafted into a war to save his descendants, and who eventually steps up to the occasion, overcoming his fear, to save his future.
White creators always miss opportunities to create resonance in an audience by making making white male characters the default. They are sorely lacking in imagination. This is the same problem they ran into when they were asked to make the Iron Fist an Asian American actor. They even had Asian American fans give them plot ideas on how it could work. That would automatically have deepened the story in a way that would have resonated with Asian audiences.
I liked The Tomorrow War just okay. i didnt love it. It didn't "wow" me, and that's becasue we've seen this story a bunch of times already. The suburban "every-man white dude, with the Black best friend" who is looking for atonement, redemption, or to reconnect with his family.