While Vegeta has shown incredible growth throughout his life, Super seems to indicate something of the opposite for his rival. At least at first. Goku’s character throughout Super has been infamously inconsistent with his own growth as it was shown in Dragon Ball. Goku started out as a naive and innocent child who knew nothing of the world outside the forrest where he grew up.
Over time, Goku was exposed to more and more of the world through his adventures, and he grew and matured because of that. While Goku always remained a hopeless idealist who always saw the good in others, he did learn and grow from his mistakes. Goku may have been ditsy and airheaded, but he was never stupid. Goku showed numerous times throughout Dragon Ball that he was the smartest person on the battlefield, even if that intelligence didn’t translate into book smarts.
All the growth and development Goku underwent as a character prior to Super was vital to Dragon Ball’s narrative, because it’s literally the story of his life. Goku grows from an immature child in early DB to an intelligent man who can use his lifetime of experience to guide his children by the end of DBZ. Goku still makes mistakes, but he’s always someone Gohan and Goten can look up to and aspire to be like.
Infamously, Goku’s development as a character takes a strange turn in Dragon Ball Super. It became a meme among the fandom that Super’s Goku had lost a great deal of his growth from throughout early Dragon Ball, and that’s understandable. In Super, Goku does act ditsier and just flat-out dumber than he did by the end of the DBZ anime. While much of the hate towards Goku’s character in Super is ultimately overblown, there’s definitely merit to the concern. There are times when he seems to have forgotten important lessons from his past, and there are moments when he seems to make mistakes he would have learned from in DBZ.
For example, during Dragon Ball Super: Super Hero, Goku sees Vegeta meditating and asks him what he’s doing. Goku seems confused as to why Vegeta would just be sitting in one spot instead of working out and training. This is an extremely strange moment for his character because Goku had meditated multiple times in the past. This scene was altered in the manga to avoid this continuity issue, but it’s ultimately just the most prominent example of how Goku has lost some of his development from DBZ.
This wasn’t just a mistake on Akira Toriyama’s part, either. During an interview with Wired, Toriyama stated that he was dissatisfied with how heroic Goku became in the original DBZ anime. That being the case, it’s likely that he purposely made Goku a bit more bubbly and silly in Super because he didn’t like how heroic he became in the original DBZ anime. This was a conscious attempt on Toriyama’s part to retcon an aspect of Goku’s personality he didn’t like, but it came at the consequence of making noticeable changes to a beloved character.
Ultimately, Goku is a character whose growth has always been subtle, because even as he has learned throughout his life, his personality hardly changes. He’ll always be a carefree and gentle heart who will get serious when it comes to a fight, and that should never change. Even so, Goku’s penchant for forgetting the lessons of his past has deservedly earned his characterization in Super criticism. In comparison to Vegeta, Goku never really had to grow much in Super anyway – he just had to remain the same Goku fans have always known and loved. In a way, he does that, but it’s unfortunate that he often forgets where he came from.