If I understand it correctly, Smalltalk is really nothing like Java and the mainstream OOP that Clojure is a reaction to.
Smalltalk, it is an experience, given that language, IDE and runtime/OS are all blended together, while Java can only do so much, even with the more advanced IDEs.
Clojure might be a reaction to C++/Java/C# OOP style, but it surely adopts Common Lisp OOP style.
I think it's worth learning, even if you never use it.