For me the biggest value they contributed with the Go standard library is the interfaces they baked into it, not necessarily the default implementations of them (no complaints there of course). They modeled the way that servers are built as interfaces, and if someone builds a 3rd party lib (like "mux", mentioned here in the comments), usually they implement the interfaces defined in the standard lib and they become a drop in replacement to the default implementation. I wish more SDKs were built like this.