That's a bit of an old-school language flame war response. It seems obvious that there is no objective criterion for determining when a language is simple enough and when it isn't. Not everybody uses Go for the same hypothetical "design space", and the implicit claim in your post that the same criteria do not apply to Rust or Zig is also dubious, as if they couldn't possibly work as languages in the same "design space." We're talking about general purpose languages. To give you an example, Rust is overengineered and way too complex for my needs, it would seriously hamper productivity. It's important to be aware that other programmers' mileages differs.
The bottomline is that it's never fruitful to argue that feature sets that go into "simplicity" do not heavily depend on subjective programmer preferences, their tasks, and the intended application domains. Programming languages are mere tools, nothing else. Choose the one appropriate for your goals.