I just watched The Lego Movie and, apart from all the random advertisement they put in there, it was a decent movie. Up until it changed from being a story about Construction worker Emmet, Lord Business, Wildstyle and all the others, to a story about some random boy called Finn and his dad, whom we know nothing about. It wasn't the first time I noticed this phenomenon. The same thing happened to The Smurfs. The Smurfs originally was supposed to be a story about, well you know, the Smurfs. And in the Smurf universe there aren't supposed to be any humans in there other than Gargamel and those from the medieval kingdom sir Johan and Peewit are from. So in the movie, the story wasn't even about the Smurfs anymore and it changed into a story about the Winslow family. So is this a trend? And if it is, what's the idea behind this?
At least in the LEGO Movie, my impression was that the actions of the LEGO characters were led by the boy. The conflicts in the LEGO storyline were the kid acting out his own conflicts with his father.
The father wanted to Krazy Glue (Kragl) all the LEGOs together so they couldn't be played with. The father considered himself a master builder, and everything had to be perfect. The boy considered himself (and Emmett) to be not-very-good builders, probably because he compared himself to his dad. But he liked to play and build and use his imagination (which had been invalidated) and that's why the Kragl was such a terrible thing to him -- it stopped him from playing and building silly things like double-decker couches.
So the way I took the movie, the boy's story had been told by Emmett and Wild Child and everyone else during the first 3/4 of the movie. The boy wasn't superfluous at all.
(I haven't seen The Smurfs, so I'm not sure if the humans were as integral or not. Another non-human movie with humans in it was The Muppet Movie, and the humans seemed kind of superfluous to me. But they gave human audiences someone to identify with.)