Something obviously went very, very, very wrong during the making of this computer animated movie. The only theory I have that might explain its general failure to entertain is the fact that it was a co-production between three very different countries - China, Germany, and the UK. With three different cultures working on the same project, it seems that it couldn't be fine tuned to be satisfying to one (or any) culture.
The movie fails in two big ways. First, there is the script. It is an utter mess. There are many things that are not explained, character development is usually near zero, and there is obvious padding. The second misstep is that it is directed in a manner that is pretty much free of passion and enthusiasm. Things plod along EXTREMELY slowly, and when there is a scene of action or suspense, the movie is remarkably casual and unexciting. Even the music score throughout is held back so much that you hardly register it in your mind.
In fairness to the movie, I will admit that I wasn't unsatisfied by its visual presentation. While the movie didn't have a Hollywood budget, the movie looks fairly colorful and detailed. But even with an acceptable look, the rest of the movie is so tiresome and badly handled that it was a real struggle for me to watch the movie completely to the end. I think even young children will get some sort of feeling that the movie is being held back in many key areas, so even they should not be subjected to watching it.