I think it is misunderstood. I it that they lost sight of the premise a little and they focused a little bit too much on the twists. But overall the seasons are supposed to represent an evolution. If they stayed in the park there would be almost zero character development. Also, from a revenge perspective, they had to leave the park because that is where the people who wronged them live. They can't simply wait for them to come back. I also like the slight Matrix twist that they might never have left the park!