As much I was grateful we got Monstropolis the Monster's Inc. world in Kingdom Hearts III and that it's now in the Kingdom Hearts franchise, part of me felt that it should've been a world earlier in the KH series like Dream Drop Distance or Birth by Sleep, instead of KH3 mainly the former game in terms of environment and gameplay value. Even I was almost to the point on giving up on Monster's Inc. becoming a KH world even after the announcement of the Toy Story world back in July 2017 at the D23 2017 Expo and prior to the December 2017 leak, and I also had a bias for Pixar to become a KH world sooner than later.

Honestly, I was expecting a Pixar world to appear earlier in the KH franchise even before the release of KH3, along with the fact that the environment of Monstropolis would've made it a suitable world for Dream Drop Distance due to the flowmotion and the theme of Dreams/Nightmares , and at the same time the theme of Fear for Birth By Sleep which in the original film, the Monster's scare children for the scream power to power Monstropolis before switching with laughter at the end of the movie and Unversed are attracted to Negative emotions such as Screams along with tying in to Vanitas as he was a major antagonist in BBS and has sent the unversed to various worlds with Monstropolis being one of them.

Now granted the reason Monstropolis was used in Kingdom Hearts III over Birth By Sleep and especially Dream Drop Distance was:

• Nomura wanted to save the Pixar worlds (Toy Story and Monster's Inc.) for a mainline game (Kingdom Hearts III) according to an interview in the KH3 Ultimania instead of a non-numbered title (e.g. Dream Drop Distance or even Birth By Sleep).
• To make use of the Unreal Engine 4 which captures the look for the Pixar and CG Disney animated films (e.g. Tangled, Frozen and Big Hero 6) over the style of the original graphics (Unity Engine) used from the first KH game up until Dream Drop Distance.
• To tie in Ventus' heart residing within Sora whom Vanitas has been desperately searching for him while he was busy being reconstructed and also having the Unversed collect the screams of the children via the cannisters from Monster's Inc. to fuel him as screams/fear is a form of Negativity and Unversed are attracted to the negative thoughts and emotions.
• Monstropolis narrative wouldn't have fit as a world for Dream Drop Distance or even Birth By Sleep respectively due to the themes, gameplay and story, along with the fact that Pixar wanted to have an original story for this world over a retelling of the original movie.

But I'm going to be honest, out of all of the Disney worlds in KH3, the issue I had with Monstropolis was that it was the ONLY Disney world that didn't dealt with or had ties with what Organization XIII were doing while they were meddling in the different Disney worlds such as the Black Box (Olympus, The Caribbean), The New Seven Hearts (Kingdom of Corona, Arendelle) or especially the Replica program (Toy Box, The Caribbean, San Fransokyo) making Monstropolis the "odd duck" out.

So honestly, I think they should've had either had another Pixar film (Brave or Inside Out) or another Disney animated film as a world over Monstropolis for KH3 as it would've tied in with what Organization XIII had been doing throughout the game while they were meddling in the different Disney worlds be it looking for The Black Box, The New Seven Hearts and especially doing research on the Replica program to fill out their missing members, even though with Inside Out it was out of the question as Big Hero 6 became the last world Nomura chosen for the world selection and on top of that their isn't any Disney and/or Pixar film that would've fit Vanitas as the antagonist of that world besides Monstropolis.

Edited July 29, 20223 yr by DisneyXPixarfan95

you know for about 4 minutes in my life in convinced myself it was gonna be in DDD. see when one of the trailers first game out the version I found was little blurred so I thought the traverse town post office was the door vault and spent the rest of the trailer waiting for mike and sully to appear. imagine my disappointment when i saw the better quality version.

but i would say monstropolis in 3 was worth the wait. its one of my favourite worlds in the game probably cause apart from a boss fight with randall it was exactly what i wanted from it. exploring the factory and racing around the door vault it was awesome. plus sulley taking on vanitas was glorious.

in regards to your own point i think the feeling of disconnect would of happened no matter where you encountered vanitas cause as you pointed out he was doing his own thing and that wouldn't have changed. but it fits into his own character rather well as in its clear that xehanort doesnt have complete control over him and he will go off and do his own thing for his own sadistic amusement