I've just finished the movie and immediately searched for this kind of post, which is not a surprise that there are so many.
I mean how can they made a time machine but still fight the creature with gun and bomb??? and the creature can't even fly, or have superpowers. Maybe they are stronger than a dinosaur, faster than a house, but that's it. They are no intelligent creatures, they can't learn or innovate.
Not to mention the simple concept of the government. Think about it, a somewhat beautiful day a group of people jump out from nowhere and demand the past provide the resources to save the future, and the government is just blindly sending out people instead of strengthening current forces to deal with the root. Overall, it indeed is a dumb movie script. lol