The plot was always there since episode 1. What they could have done better is showing us more and more about Coconas dream and thus making the audience more interested in this mystery.
Also I agree that most criticism about the later episodes are stupid, the production wasn't as stellar as before as well. Yayaka vs plant-loli still looked amazing, but the fight against Mimis skull-tentacles was basically just key animations. There are a lot of smaller things, like the awkward fall from Salts bike.