When I was small I created many things with legos, and erector sets which I alone had imagined. I built these things because I was young, and it pleased me. I don't feel they were any less genuine because I didn't create the plastic or steel that went into producing them. I don't feel that the paintings I've done in my lifetime are any less genuine because I didn't collect the ingrediants that went into the paint, or the paper. I don't imagine a sculptor feels his work to be less valid because he didn't make the marble he brought to life, and I'm quite sure the animators at Pixar don't feel their work isn't as good as the amateur who makes all his own models, as hey haven't the time,  the making of the models is the modelers job, the rigging the riggers, etc*.* I don't see the logic behind their argument. Perhaps they are Nihilists.