Dragon Ball Daimahas gotten a lot of criticism for its retcons, which have caused continuity issues withDragon Ball Super. However, most of the retcons made for the series make perfect sense for the storyDaimawas trying to tell.
Dragon Ball Daimais set in the narrow period between the end of the Buu Saga ofDragon Ball Zand the beginning of the Beerus Saga ofDragon Ball Super. As a result,Daimais itself a retcon, taking a period where previously nothing was believed to have happened and showing that there was, in fact, an adventure in there. Anything it changed would have an impact onSuper, and it would be difficult to tell a satisfyingDragon Ballstory without upsetting the status quo in some way.

Daima’s Story Needed a Climactic Transformation
Pretty much everyDragon Ballstory that exists ends with Goku attaining a new transformation which helps him to win the day. New forms are one of the most exciting elements ofDragon Ball, as the characters push themselves to the limits to defeat evil.WhileDaima’s inclusion of Super Saiyan 4may have been met with some groans due to the continuity issues it created, the actual use in the story of introducing the new form is extremely effective. It fulfilled that exciting moment, and disrupted things quite a bit less than pretty much any alternative would have.
Imagine, for a moment, if Goku’s fight against Gomah didn’t involve a new transformation. Many fans would’ve been quite disappointed, and it would’ve made the fight seem too easy. After all, if Goku’s existing power was enough to defeat the villain, then was there ever really a threat? By forcing Goku to reach a new level, it emphasizes the power of the villain.

Dragon Ball Has Always Been Full of Retcons
Dragon Ball’s Story Has Been Retconned Many Times
Many of the fans who are upset aboutDaimaseem to be upset because Toriyama didn’t pay enough attention to canon to avoid these retcons. However, Toriyama has always been prone to using retcons in his storytelling.Goku’s origin, for example, was a complete retcon; he wasn’t intended to be a space alien from the beginning, and the same is true for Piccolo. Vegeta’s initial characterization was radically changed to fit with the fact that he was actually working for Frieza, and that was arguably the best change the manga ever made.
While retcons can be irritating to fans, it’s clear that they aren’t always a bad thing. Akira Toriyama wasn’t the type of writer to let continuity tie his hands with the writing of a story, and that’s a big part of what makes him such a great entertainer. Getting upset over retcons won’t change their existence, but it can affect one’s enjoyment of the material. It’s easier as a fan to just relax and not worry so much about retcons, and just enjoyDragon Ball Daimafor what it is: a fun adventure with Goku and friends.