Okay! Some of my thoughts on Islands of Adventure first.
Easily my favorite park out of the two, due to both the intricacy of the theming and the collection of attractions. In a way, each of the islands almost feel like proto-Diagon Alleys, in that they are somewhat separated from one another, but not immersive to the degree of blocking out sightlines from other islands or fully committing to the reality of the location.
Hogsmeade, however, looks beautiful from almost everywhere within the land. One thing I never realized before visiting was that you could see the castle jutting out above the village when you entered the land. That, along with the addition of the forest grounds and the abandoned abbey of Hagrid, truly wowed me.
I also think Hogsmeade helped me realize something about theme park immersion that I hadn't considered. Although accuracy to the source material may be important, depth and movement truly help to convince you that you are in a real place, rather than a series of facades. I hope Epic Universe takes that lesson to heart, not only by creating lands with kinetic elements but also by suggesting places and objects outside of the park space (like with the spires placed on the show buildings in Galaxy's Edge)
As for the individual lands...
Jurassic Park: Not much to say as JPRA was under refurb. I did briefly get lost in Camp Jurassic, which seemed expansive and dangerous in a way no other play area does. I appreciate that Universal has these structured areas for kids to have their own adventures. Beyond that, the land really hurts without its signature attraction.
Toon Lagoon: Not as bad as I thought it would be. Loved the Popeye area and ride and was charmed by the cheesiness of the Comic Book Alley. Dudley is a dud though, and I wish it was as good as the view from the bridge makes it out to be. I would honestly mourn the loss of this land. I think the aesthetic could work if the theming throughout the land iterated on Popeye's successes and if the main thoroughfare was made more aesthetically pleasing. Also put something in the theater, please.
Lost Continent: Also needs something new in the Sinbad theater. Was actually able to peer into the theater space from the Hogwarts Express line and was surprised to see that all the sets are still there. Regardless, definitely my second favorite land in the park after Hogsmeade, and the rockwork obscures the length of the pathway. Poseidon's Fury is fun too, and that water tunnel is a trip. As much as I liked the aesthetics, there wasn't much to do.
Skull Island: Around this point I was getting tired of walking through caves to get on rides, but despite this Kong was good fun. It may use the tram tunnel ride system, but it makes up for that with the off-roading section and animatronics. It was kind of like a slow, less exciting version of Indiana Jones, which is still fine in my book.
Marvel Super Hero Island: Best rides, best music, worst food.
Suess Landing: Least favorite land. Just felt kind of stale, but not a bad land in the slightest as it offers a lot for little kids.
Hagrid: One of the best rides I've ever been on period and contender for my favorite ride of all time. Strangely, I found it more thrilling than any Six Flags coaster just because you unconsciously immerse yourself in the ride every time. Just being in a motorcycle immediately makes you want to lean into the turns and get close to the water/rockwork.
In summary, it's amazing that this park has so many dead spots yet still feels like one of the best parks every made. However, if they do decide to turn Toon Lagoon and Lost Continent into Lord of the Rings or Hyrule, I do hope they emphasize some of the stranger elements of those properties. Given the variety of theming present in modern day Islands, I would hate for the park to become Fantasy Forest: The Theme Park.