First and second half of the film have a totally different tone
Characters were over the top and cartoonish in the first half of the film. So many eccentric people arrive in scenes. This provided a buffet of entertainment for Enid to smirk at. But then the tone changes...
The more time goes by, the less ''funny'' everything becomes. The world seems to settle into a much much serious and semi bleak place. No more eccentric characters. Friendship's deteriorate. This could be interpreted as seeing things from the perspective of Enid. The high school fun and games are over and the real world, the adult world, or the '' ghost world'' just isn't much fun anymore.
This is a pretty good interpretation of what it's like the enter the adult world. It's a smack in the face.