Not disagreeing with the sentiment, but I dislike the word "simple" used to describe languages, because it has two meanings: simple = "consists of few parts" and simple = "easy to use", and these are not the same.
Certain things in Go are not easy (not simple), because Go has few language features (is simple).
Go has definitely a lower barrier to entry and is very productive for certain size and complexity of a project. However, as you start pushing beyond "scale" Go is designed for, Go becomes less simple to use. To appreciate things like generics, non-nullable types, no shared mutable state, you have to be working on a problem that requires these things, and only then these extra features pay off and make development and maintenance easier.
Certain things in Go are not easy (not simple), because Go has few language features (is simple).
Go has definitely a lower barrier to entry and is very productive for certain size and complexity of a project. However, as you start pushing beyond "scale" Go is designed for, Go becomes less simple to use. To appreciate things like generics, non-nullable types, no shared mutable state, you have to be working on a problem that requires these things, and only then these extra features pay off and make development and maintenance easier.