I have to disagree with Lucy's character overreacting. Honestly, I've known people that behave like that. Showing their feelings, reacting strongly to happiness or sadness. I think it contrasted well with Tim who was, well, very let-down and depressed. The villains, well, that I guess I can agree, sort of. But overall, it was a great movie!
Now that I've finally seen the movie, I agree with your review overall! In general I loved it and would definitely be interested in seeing it again if I knew people who were going. Pikachu was adorable and seeing all the Pokémon brought to life gave me so much joy.
Lucy's character did feel a bit childish and 'Spy Kids'-esque as was mentioned, but thinking on it now I think it's because the pacing of the entire film was so fast (my biggest issue personally) that I felt I couldn't get to know the characters as much as I would have liked. Something like this would have been perfect being broken up into a three-part movie series, to give us more time to understand and bond with each character. I get Darkmaster006's point above but am not surprised being thrown right to a character with such exaggerated personality traits was exhausting.