The age range you have there is probably a bit more accurate than my source, but you can't ignore the fact that Monsters is probably the least anticipated by the GP, which could turn around though, for better or worst.
The GP still doesn’t know what’s coming to the new park. I’d wager the majority of the GP doesn’t fully grasp a new park is even coming.
But, beyond that, let’s look at:
IoA - JP was THE draw. It was the S-class IP. Seuss and Marvel were B-class while Lost Continent, not having an IP, was a low C-class.
Animal Kingdom - This is an odder park. Pretty much, the only “IP” it had for itself at opening was Lion King. Tough to be a Bug and Dinosaur both predated their IPs. The big draw was generic - “animals.”
MGM Studios - At opening, it had Beauty and the Beast and Little Mermaid. Those were its big IPs. Star Wars and Indiana Jones, though big, weren’t as big a draw for the target market.
Universal Studios - The big draw at opening? Nickelodeon Studios. Really. Kids going to Nickelodeon was the bread and butter of the place. Most kids had no clue about the other IPs, apart from Jaws, which wasn’t really open, and BttF opened a year later (it then became the secondary draw).
VARIETY is key. Variety is what enables a park to appeal to the broadest range of guests. No aspect of the GP is homogeneous with regard to interest in a property. Let’s look at it this way.
SNW - Broadest target. Aimed at 6 to - 45. Great for attracting families regardless of ages.
Harry Potter - Smaller range, but still fairly broad. Aimed at 15 - 35. Good for families with teens who grew up with the books.
Dragons - Broadly accessible, but FOR kids. Target is 3 - 12, but viable to marketing to 3 - 30.
Monsters - Looking at the target ages, there’s a massive range missing, which is older than 45. So, older parents and grandparents. That’s what Monsters is for. It’s for them.