I've never seen a Rails application that suffered from too much decoupling. If someone out there wrote one of those, call me because I have a job for you. 99% of all things written in Rails are monolithic messes of business logic encrusted with persistence and response handling. So ridiculously coupled that you don't talk to objects by themselves, but bring in a whole family of resources to models and controllers that violate almost every SOLID principle.
The whole "You're not gonna need it" argument works until you actually do need it. Which, unless you're not doing a good job, is going to happen. Then you have no discriminated interface to pry your application blocks away from each other and can't persist a model without dozens of unintended side effects.
There's no readability penalty to decoupling. The more you decouple the less you need to read to understand an application.
The whole "You're not gonna need it" argument works until you actually do need it. Which, unless you're not doing a good job, is going to happen. Then you have no discriminated interface to pry your application blocks away from each other and can't persist a model without dozens of unintended side effects.
There's no readability penalty to decoupling. The more you decouple the less you need to read to understand an application.