Dragon Ball Super proves that the Buu Saga could easily have been avoided - if the characters had just made the right decisions. In Dragon Ball Z, the Buu Saga brought more chaos and destruction than any other Dragon Ball story ever. The arrival of Buu resulted in the deaths of most of the heroes on the show, including the obliteration of the Earth itself.
Toward the beginning of the Buu Saga, Goku, Vegeta, and Gohan were recruited by Supreme Kai to stop the sorcerer Babidi and his chief minion Dabura from releasing Majin Buu. After several long battles, it all came to a head when Babidi convinced Vegeta to side with him instead by giving him some of his power. After joining forces with Babidi, Vegeta fought Goku, and their combined energy allowed Majin Buu to break free of his seal. Vegeta saw the error of his ways, but by then it was too late. It came to a point where the heroes had to lean on new techniques to win. Goten and Trunks fused to become Gotenks, Gohan unlocked his full potential, and Goku and Vegeta used the Potara Earrings to become Vegito. It wasn't until after the Earth was destroyed that Goku was able to beat Buu with a Spirit Bomb.
In Dragon Ball Super, Goku and Vegeta encounter Future Trunks, who they last met in the Cell Saga. He catches them up on what's happened to him since he returned to his timeline to defeat Androids 17 and 18. In his timeline, all of the other heroes are dead, which means that when the world is threatened, Trunks is on his own. Apparently, Trunks had to deal with the coming of Buu as well, except he handled the situation quite differently. The same was true when the threat of Buu emerged. A flashback explains that Future Trunks was warned by Supreme Kai, so he intensified his training.
When the time came for him to face Dabura and Babidi - just like Goku, Vegeta, and Gohan did in Dragon Ball Z - Trunks fought Dabura one-on-one, and managed to kill Dabura and Babidi at the same time. Trunks' swift victory stopped Buu from being released. Thanks to Trunks, the Buu Saga never happened in his timeline.
What would have happened if Goku, Vegeta, and Gohan had stuck together and just killed their opponents? Though Trunks was strong, it's doubtful that even with his increased strength that he was stronger than Goku. If they worked together, the three could have averted the Buu Saga with ease. It's a reminder that Vegeta's pride and desire to beat Goku is really what caused the Buu Saga to occur in the first place. If the heroes had made better decisions, they never would have met Buu at all. Trunks dealt with this problem without help, and yielded much better results.