The difference being that objects have a class where you can look to see what fields it specifies.

Java doesn’t really have a nice interface for interacting with objects in general. Closure does have a nice interface for interacting with dictionaries. They have namespaces keyword symbols for keys which are much more ergonomic than typing strings, and they have lots of functions for modifying dictionaries. I think the big difference is in the philosophy of what the language thinks data is, and how the world ought to be modelled.

Sure, depending on the language. What I mean is having dictionaries doesn't mean you don't have to learn schemas.