One of the reasons the animation of the characters looks so creepy is they used adult actors (Peter Scolari, Tom Hanks) to motion capture the performances of the child characters. So, the child characters have an odd look because children just don't look, act, or move the way adults look. The children in this film look like little old men and it is creepy. They should have used children to motion capture the performances.
shareThe main character is played by a kid, LOL.
And adults have been voicing characters who are kids in both TV and movies since each was created.
The main character is voiced by a kid, as are the other kids, but they are all still mo-capped by adults.
Adults, typically women, have voiced kids in cartoons that don't usually involve motion capture.
Big difference.
I agree with the OP, it would've been better if the child characters were voiced and mo-capped by kids, their movements and facial expressions were off at times.