Deadpool 2 follows Wade learning about what it truly means to be a hero and follows the theme of how it's not necessary to be a perfect bastion of justice and goodwill every day and how it's important to just take the time to recognize when and how a person can make the choice to do good.
This puts him in conflict with a much more aggressive "hero" Cable, who is trying to save the future by going back in time killing a child that will grow up to be the strongest terrorist of all time. Deadpool spends the entire movie risking it all to save a child because thats the right thing to do. He makes his choice and does it. This story runs in parallel to Colossus' story arc, where he learns that while being a just hero is important, sometimes in order to do right you have to get your hands dirty and can't be the chivalrous knight that he's portrayed as in the movies at all times. Both characters are at an extreme of each other and learn to meet in the middle to save, not the world, but the life of one child (and a bunch of kids that were being experimented on).
Despite the fact that high concepts like time travel are employed, it's not the main focus of the story allowing the story to stay personal and low key. If Pool just stepped aside and let Cable kill the kid, the world would have been saved. He knows thats not right and he goes out of his way to insert himself into the adventure to save that kid AND the world. It's not the greatest story of all time or anything, but it's surprising how much care for what Deadpool is and what a hero is put into the movie.
