Here's something that most of the fanbase watching don't exactly understand or consider when critiquing these kinds of shows:
Shows like this get critiqued as if the final product was all one unobstructed conscious choice on the creator's part. If a show has multiple IPs, that usually means that the creatives also had to run all of their concepts and ideas through multiple teams of IP holders and brand protection people who work for the production companies who own the films. At Disney, even though they own almost everything they use, they STILL have to run through teams at Pixar, Lucasfilm, and other third parties and partners to get ideas for show concepts approved. These people usually are marketing people that have a very hard time understanding theme park rides and shows and how they are different from film or tv. Every show I have worked on had a frustrating process of bouncing ideas back and forth until we got approval from all sides.
As an analogy, a show is like a new car you want to deliver, yet on the journey from the factory, it goes through several major hailstorms. Success is when if you get the car it still looks like.... a car.
Looking at this show, I see at least 6 different IP holders that all must have had to approve this. Most impressive to me is that they were even allowed to have a Harry Potter section in this show at all! Warner Bros. is notorious for being very protective of how that brand is used. Many IP holders don't want you to put their IP next to other brands, etc. The list of requirements almost makes it impossible.
Half the work of a show like this is fighting to keep your creative ideas intact as it gets beaten to shreds by marketing people who just would rather you make an advertisement or movie trailer.
Looking through the lens of my past experience, I am blown away at how they got all of these properties to work together. The show flows together through the use of the music. While there isn't a narrative that ties it together, the way the music was strung together is pretty masterful. Getting the IPs to approve just that must have been a nightmare.
So if I had to guess, putting on my producer hat:
1. Jaws, BTTF, and Monsters weren't included because DreamWorks and Paramount didn't want their properties to be included next to "old" things.
2. HP couldn't tell a narrative story due to that being considered "lateral" content. They were most like pushed to make an overall brand statement or not get approval.
3. Illuminations and DreamWorks probably fought over how much their content was represented against each other.
4. There were probably one or two segments that didn't make the show due to lack of approval.
And finally 5. The lack of an overall narrative storyline is most likely due to the fact that these IPs would never let their properties blend with others in a new story that dillutes their original intent.
So look at it through that lens and this show is a pretty stellar feat of showmanship, artfully presented together with beautiful moments and some of the best music choices I've heard in a long time.