It's quite difficult to simplify an existing language, even when adding a feature could theoretically simplify a language. For instance, higher kinded types are

It's quite difficult to simplify an existing language, even when adding a feature could theoretically simplify a language. For instance, higher kinded types are simple in principle: it's just removing an arbitrary restriction about what you're allowed to pass to a type constructor. However, when adding them to an existing language it doesn't always work that way. In the limit of removing type system restrictions you end up with dependent types, which are very simple in terms of the number of type system rules that they require, but try adding them to Java and you'll get a monstrously complicated beast.