This movie is really about the journey of a girl who always questioned why. It's easy to get distracted from the main objective through beautiful art and animation. They also derail you on purpose through romance. You're supposed to feel lost like Suzu till the final song which should tie everything together.
I throughly enjoyed it, but I can understand why others would be put off. It's complex and has a lot of deep meaning. This movie needs to be watched a 2nd time to fully appreciate it.