They said Gantu didn’t work, but I’m guessing they scrapped him for time. I think they wanted to gut the space side of the movie to focus on the family side. The family side is bolstered, though I wonder how lacking it is if hadn’t watched the original. While I believe Gantu isn’t itself a loss, I agree that it moves that villain hat to Jumba making him a full character. My guess is that human-izing serves two purposes: to downplay the cartoony CG in a live-action remake, and to give the actors on-screen time which costs production more money but makes it worth the time for the talent. To be honest, it’s kind of messy though, you have a well known comedian in a supposedly funny scientist role, who just comes across as angry, gun-happy guy wanting to finish the job. Original Jumba is deceitful to authority rooting for Stitch as a villain, and then as a semi-paternal figure like everyone else.