It's not really about them "taking care" of Sora as if they're his parents. Donald and Goofy are his friends, plus we need major Disney characters into the game somehow.
Sora was treated like a moron in DDD because he was actually a moron lol. Sora isn't known for his intelligence in past and future games, that's true, but DDD Sora is notorious in the fanbase for being a clueless moron.
Also isn't everything you are saying his entire arc in 3? He briefly thought he was nothing without his friends, only for Riku to snap him out of it, and then decided to get Kairi by himself. KH3 has some spotty character development, but I thought that was simply the point. It doesn't seem like he has any immense reliance on Donald and Goofy, they're just his friends and they enjoy going on adventures together.
That's true, Sora's not known for his intelligence, and that's fine, but if there were levels of stupidity, then DDD would be the highest for Sora, in KH1, Sora was actually pretty smart, when Sora found out what Riku was trying to do to Pinocchio, he realized Riku wasn't the same friend he had known on Destiny Islands, he knew at that point that Riku wasn't on his side, and had to be stopped, or at least knock some sense into him, and Sora from KH1 and KH2 were the lowest level of stupidity, COM not so much, everyone says he was smart in this one, but I don't see it, he got angry and wouldn't think things through, in fact when Donald and Goofy suggested thinking ahead, Sora for some reason thought they meant abandoning Namine, as if he had never heard of the phrase before, a smart person would have realized that they were right and listened to them, and I'm not saying cut them out of the game entirely, just for them to have a similar role that they had in recoded, and KH3 had the best Sora so far, he doubted himself, which is a very human thing to do at times, but when he and Riku were the only ones standing, he gave up, that shouldn't have happened, sometimes I like to imagine that it never happened, and this led to the worst use of time travel in the series, yes he was grieving, he had just lost almost everyone important to him, (actually this just gave an idea, I'll post it in another thread), but there were still people and worlds that were still alive to be saved, he and Riku should have stopped Xehanort then grieved, and Aqua was no better, clearly she was suffering from PTSD, she was stunned by how many heartless there were, and she wasn't even seeing heartless, she was seeing multiple copies of herself as Anti-Aqua, and lost her nerve, and everyone else wasn't doing any better Ethier, they should not have had such a hard time with Terranort with how many of them there were, but I digress, nothing in the previous games indicated that Sora would ever give up, maybe that one time he and Riku got stuck in the realm of darkness, but that's only because they were sure they were never going home, and there's this quote that I have memorized ever since I got into a certain franchise, and it goes something like this, "the needs of the many outweigh the needs of the few.", Sora may have lost the people who were closest to him, but that's no reason to give up, especially when so many people are counting on him, for the record Sora is my favorite character in this series.