They have a well considered argument that adding generics into the language will add to it's complexity, so much so that the power of the feature will be outweighed by the complications that the feature brings. What proponents of generics say is that the core team is not properly considering all the benefits of generics. The language's surface will be simplified, your code as a consumer will be easier to write, and even that Go already has generics but only for certain blessed types that are built into the language.