You know, for all the effort we are putting in to reviewing these movies, I think that we must remember that these movies are directed towards kids. The writers probably weren't too concerned with the plot, but more about entertainment of little kids.
THAT is still NO excuse. Even kids movies can have great plot and storytelling. You just need to find the right writer, editor, producer, director, etc. All of which can be rather difficult to get.
You're forgetting the most important part of making a good kids movie: You actually have to put effort into your work. As cliche as this may sound, a good story and good characters aren't hard to make. You just need to have some imagination. Something I think a lot of kids movies today are severely lacking in.
One thing I don't understand is why so many kids movies today are so sugarcoated and safe. When I was a kid, I was growing up with The Land Before Time(obviously

), Batman the Animated Series, Dragon Ball Z, Tenchi Muyo and Yuyu Hakusho. Hey, I was watching Adult Swim by the time I was nine. Those weren't the most kid friendly of shows but I enjoyed them and I turned out just fine. I don't think there's anything wrong with exposing kids to more mature themes such as death and maybe even parenting. Most of the things that adults try to cover up are things that kids are going to need to learn eventually when they start to get older.
I think it's possible to make a kids movie with a good story, maybe even a great one. It just seems like most studios today would rather focus on "how fun" a kids movie is or "how super duper cool the 3-D looks" than actually focus on what truly matters: the characters and story. Pixar and How to Train Your Dragon proved that you can have kids films that are fun yet still have a good story.