Having seen it, I am less surprised it is doing so poorly and received the reviews it did.
I saw it with a friend who likes Disney but wasn't aware of the film's reception, and we both walked out feeling that everything that happened seemed a little un-earned, if that's the right expression.
For a start, life in Rosas didn't seem that terrible to begin with, so the stakes at the centre of the film seemed more "I guess that's an issue..." than a great injustice that needed resolving. Except for one mopey character, everyone seemed very happy and eager to move to this land of tolerance and diversity with no taxes and we both left wondering whether Asha was screwing it all up so people could regain the knowledge that they wanted to be able to fly or compose songs. Perhaps that says more about us, though!
The evolution of characters like King Magnifico, Asha, the Queen, and indeed the entire population of Rosas also seemed very quick and a bit hard to understand. For example, as best I could tell the King's issue was one of power corrupting. He was treated within in the film more as innately evil, however. How Asha went from being nervous to have an interview with the king to leading a revolution against him in what seemed like a split second was also a little mystifying. I'll be honest and say that I understand the criticism of her basically emerging fully-formed as a hero without any convincing inner-struggle or evolution. The goat also has to be one of Disney's most forgettable animal sidekicks/comic relief characters.
Overall, I was a little surprised at how undercooked everything seemed even after having read the reviews. Best I could tell, the message was something along the lines of not centralising the power of deciding what wishes are valid and should be granted but rather devolving that power to individuals to decide for themselves. That's all fine as (I guess) a pro-liberal democracy message, but I feel that they signed off on the film too early in the development process before they had really fleshed out the world and the motivations of the characters.