> What's funny is seeing languages like Java trying to "undo" the arguable "mistake" of abstract classes by adding more and more power into interfaces: default methods, etc.

Default methods are how Java-like languages are able to have mixins. They are extremely handy and quite safe to use as far as I can tell.

golang on the other hand shows its extreme weakness in modeling non-trivial domains, and the code base quickly becomes very verbose and tedious to work in.