The simple answer is that it was announced as one. The more complicated answer is that, traditionally, systems programming languages were those which are not s

The simple answer is that it was announced as one. The more complicated answer is that, traditionally, systems programming languages were those which are not scripting or assembler languages. If you listen to Pike for more than a few seconds you'll soon notice that he's a bit of a language purist, so whatever modern interpretation you might have for a term is unlikely to match what he is communicating. More specifically, it was announced as a systems programming language designed for things like web servers and systems of that nature, with more control than Java in some areas. Even with conflicting definitions of systems, there should have been no illusions about it being designed to be in roughly the same space as Java with that context. It was very much suggested from the onset that it was meant to compete with Java. But, ultimately the game of telephone truncated the context that would have helped with finding the right definition of systems and, I expect exacerbate things, there was Rust coming onto the scene juicing the situation with its fans often claiming that "Go isn't a systems language, Rust is!" leaving some revisionism about people believing that Go was a systems language (in the modern sense).