I agree with all this, too. But, I don't see how the Disney worlds in KH2 were any more random than the ones in KH1. You're looking for Riku and Keyholes and fighting baddies... isn't it the same thing?
Although I love KH2, I agree that the Disney plots didn't connect to the overall plot like KH1 did.
And it wasn't really the same thing, actually. xD
KH1: Overall plot includes SDG as protagonists; Maleficent, Hades, Jafar, Ursula, Oogie Boogie, and Captain Hook as a group villain; Riku as an antagonist; Ansem SoD as overall villain, taking over that role after most of the group villains are destroyed (the group villains WERE the main villains for the majority of the game, though); Sora searching for Kairi, rescuing the PoHs, sealing Keyholes; Donald and Goofy searching for the King, and aiding Sora in his quest.
Disney World Connections of KH1:
Traverse Town: Big connection - world plot revolves around what the main villains did the TT's inhabitents, and the world serves as a sort of base for SDG
Wonderland: Small connection - world plot centers around Alice, a character who is important to the overall plot, and her kidnapping that aids the overall group villains
Olympus Colliseum: Very small connection - the main villain of that world is part of the overall group villains, but the world plot doesn't connect to the overall plot
Deep Jungle: Very small connection - SDG discover keyholes, an important aspect of Sora's journey, but otherwise, the world plot does not connect to the overall plot
Agrabah: Big connection - the world plot centers around helping Aladdin save Jasmine, and the whole world plot has to do with trying to stop the aid of the overall group villains, so the world plot is a HUGE connection to the overall plot, since, if the world plot was taken away, so would a good chunk of the overall plot (taking away the world plots of the first three Disney worlds would only take out small bits from the overall plot)
Monstro: Moderate connection - the world plot centers mostly around the dividing friendship of Sora and Riku, and their search for Kairi
Atlantica: Big connection - the main world villain is part of the overall group villains, and her actions in this world center around her cause that would effect the overall plot
Halloween Town: Big connection - the main world villain is part of the overall group villains, and his actions in this world center around his cause that would effect the overall plot
Neverland: Big connection - the main world villain is part of the overall group villains, and his actions in this world center around his cause that would effect the overall plot. This world also shows the evermore dividing friendship of Sora and Riku, and their shared cause to save the lifeless Kairi, whom Riku has found. Plus, it touches a bit on the subject of the PoHs, a big part of the overall plot.
Hollow Bastion: Big connection - the world plot basically IS the main plot, as everything that happens in this world has to do directly with the overall plot (Kairi, Riku, Ansem SoD, the plans of the main villains and their demises, the PoHs, the final Keyhole, you get the point)
End of the World: Big connection - same as above, the world plot basically IS the main plot, as everything that happens in this world has to do directly with the overall plot (Ansem SoD and his demise, the destroyed worlds)
KH2: Overall plot includes SDG as protagonists; Maleficent and Pete as side villains; Organization 13 as main villains; Sora searching for Riku, trying to stop the evil deeds of Organization 13, stopping the few misdeeds of Maleficent and Pete, and saving Kairi from the main villains; Donald and Goofy searching for the King and aiding Sora in his quest.
Disney World Connections of KH2:
Twilight Town: Big connection - the world plot has almost everything to do with the overall main plot, mainly the secrets revolving around Roxas, as well as serving as a bit of an information source for other things (Kairi's kidnapping, Saix's introduction, the news of Axel betraying the Organization), and the world is what leads SDG to The World That Never Was
Hollow Bastion/Radient Garden: Big connection - the world plot has almost everything to do with the overall main plot, mainly the secrets revolving around AtW and Xehanort, both of him are a big impact on the story (hell, the mysteries surrounding them are half the story)
The Land of Dragons: First trip - no connection. Second trip - moderate connection - Sora gains small clues concerning the whereabouts of Riku, and Organization 13 attacks this world for their own purposes, which Sora must put a stop to
Beast's Castle: Big connection for both trips - the world plot centers around what Xaldin, a main villain, has been doing, and finally ends in his demise
Olympus Colliseum: First trip - small connection - Demyx makes a small cameo and causes minor problems for the protagonists; Pete makes a slightly larger cameo by taking Meg hostage to help Hades, but his actions have little to do with his and Maleficent's plans. Second trip - no connection
Disney Castle: Moderate connection - the world plot centers around Maleficent's plans with Pete
Space Paranoids: No connection - (I feel an explanation is needed as to why, since it effects Hollow Bastion/Radient Garden, which is a big connection) nothing that happens in this world has to do with the main antagonists or aiding in SDG's quest to find Riku, the King, and Kairi
Atlantica: No connection
Port Royal: First trip - very small connection - Pete makes a small appearence, his goal to recruit the world villains. Second trip - moderate connection - the world plot this time centers around Luxord and his actions in this world for the Organzation
Agrabah: First trip - small connection - Pete makes a slight appearence and brings forth the first bosses, but his actions are minor. Second trip - very small connection - the Organization is briefly mentioned as wanting to turn Jafar into a heartless, but otherwise, no connection
Halloween Town: First trip - small connection - Maleficent makes an appearence and revives Oogie Boogie as part of her plans. Second trip - no connection
Pride Lands: First trip - small connection - Pete makes an appearence with the goal of turning Scar into a heartless to aid him and Maleficent. Second trip - no connection
The World That Never Was: Big connection - the world has EVERYTHING to do with the overall plot, since this is the home of the overall plot villains, as well as the place where they all meet their demise, and Sora finds Riku and Kairi before the three are FINALLY able to return home together
See? The connections of the Disney world plots to the overall main plot are minor compared to KH1. They hold little to no relevence to the main plot of KH2.