I'll try to keep this one actually short. I watched "Finding Dory" on Netflix last night, and... it was fine, I guess. I think I came into the film with a net neutral opinion: I'm inclined to support Ellen DeGeneres in a lead role, but I also thought her character in Finding Nemo was pretty one note. She's given a bit more depth here, but overall, there's not a lot of depth to go around.
Elevating the sidekick to the main act isn't an uncommon choice for a sequel movie, but it is more uncommon for a sequel that gets fully supported by the studio. You can point to a lot of Disney products that spawned sequels, but the sequels themselves are almost always treated like spin-off products. I wouldn't say the world of Finding Nemo had a story left in it that was screaming to be told, but Finding Dory's premise--that Dory has remembered her parents, and wants to try to reconnect--is fine.
The format is more or less the same as the original--you have two groups that are majorly separated from each other, and both have adventures trying to get reunited. In the original, it's Dory and Marlin and Nemo; here, it's Dory and Marlin and Nemo. They meet occasional threats, but mostly just complicated scenarios, and a lot of colorfully weird ocean life. There's even the sidekick who steals the show--Dory in the original, and Ed O'Neill as Hank the octopus here.
The movie's approach to disability is kind of mixed. On the one hand, Dory's memory loss is presented as a condition she has to learn to deal with, and a lot of her flashback scenes with her parents involve them helping her develop strategies for that. That's... well, realistic isn't the right word for a movie where fish can breathe in any sort of water regardless of salt content, and a father fish calls his daughter cupcake in a world that clearly has no reference for him to do so. But at least it shows disability isn't a burden, but a part of your life. On the other hand, it's also strongly implied that if she works hard, her problem will go away, which is less reflective of real experience.
There's also an interesting tension between humans and animals here that never quite gets resolved. The marine center Dori's parents lived at focuses on "Rescue, Rehabilitation, and Release," which is nice, and suggests a virtuous, ethical approach to marine life that emphasizes human responsibility to take care of those who we can. (Would that our own healthcare start with such a philosophy.) But it's worth noting we're told about this mission by Sigourney Weaver, and the celebrity involvement with the center illustrates how commercialized it is. Is there a conflict between caring for sealife and profitting off of them? Given the mass escape at the end of the movie, it seems to imply there is. (though surely some of those sea creatures were *not* suited for a return to the ocean, and just as surely, there was some human death involved in the octopod's aggressive driving. If nothing else, someone's going to suffer for the loss of the truck.)
The film raises these issues, but doesn't go very far out of its way to say anything about them. It's just a backdrop for general goofiness. And it does that goofiness pretty well, all things considered.