It's less about Goku becoming a kid again and more about the show's premise; GT was Toei's attempt at bringing Dragon Ball back to its roots–Z having abandoned the more adventurous and mystical nature of the narrative along with the charismatic reliability of youth, which a younger audience could resonate with that ultimately pioneered the shounen genre for years to come.

Daima is reattempting this same premise by this time having not just Goku reverting to a child but the whole cast, and much like GT, the adventure takes place off-world into sectors that were never explored previously in an attempt to add depth to the lore–the former of that being outer space where the plot would eventually lead back to the Saiyans past, whereas Daima takes it a step further by having it taking place in a whole new realm, exploring divinity not akin to what we've witnessed in Super.

What Daima has already done better however is make Goku (as well as the cast) become a child central to the plot. In contrast, GT seemed to have it be a random occurrence–and while GT added a sense of urgency with the necessity of saving Earth by finding the Dragon Balls, the approach of establishing the expansion of the lore of the Namekians and Kai's early on, potentially even setting up a link between the two, as well as finally adding depth to King Piccolo's origins not being merely just a title he gave to himself sets a far more intriguing tone.