I don't personally agree with him, but he makes a lot of valid points.
The biggest problem I have with his video is that he says that Sora was ruined by the whole "Keyblade being handed down) thing. Sure, it's always been really cool to see that Sora was the one that the Keyblade chose in the end, but we find out in KH1 that Riku was supposed to be the wielder, not Sora. Back that up with the fact that Sora is only a valid candidate because his heart is merged with Ventus's, and you realize just how heroic and legendary Sora is.
Also, while the story might be convoluted, the story leading into KH3 is actually simple to sum up: Master Xehanort is gathering 'followers,' and when the time comes he will try to forge the x-blade. Sora needs to gather seven Keybladers to fight him and stop him from bringing about the Keyblade War.
Keep in mind though, I'm biased because Young MX is one of my favorite characters, and we wouldn't have him without this convoluted mess of a story.