Well, they totally screwed up on making Jar Jar believable. The Jar Jar is the key thing is revealing, because Jar Jar is the key to understanding TPM's mentality. TPM lacks conviction in its own imagined world and doesn't try to make things believable. Jar Jar and the other cartoon characters (most notably Boss Nass) are the most obvious manifestation of this unreal mentality. The prequels in general don't feel real and also tend towards artificiality and lack of sincerity. TPM is where it starts, not as bad as in the later two but very much a problem.