David Gavilan’s review published on Letterboxd :
Not sure why this film has so many bad reviews. I think the characters are cute, the story is good, and the way the story is told through dreams and the magical world is very entertaining. I also had fun trying to interpret what were the things or characters from the magical world in the real world. I'm not going to spoil it giving my interpretation, but I feel from some other reviews that people didn't attempt to interpret those dreams and that they expected the film to explain them. Thus the disappointment, I guess.
I'm also puzzled by some comments saying this is like every other anime. I think this is better than the average anime. But in general, most anime films have quite interesting and original stories, compared to, say, the average multibillionaire Hollywood superhero reboot movie. That doesn't mean every anime film needs to be a masterpiece. They are just pieces of entertainment. If you are more entertained by Hollywood movies than by Japanese anime, it's OK to give up on anime. Not sure for what reason people would torture themselves watching something they dislike just to write a review here saying "meh, all anime is the same".