I suppose exclusively structural typing would be more acceptable if Go supported _real_ interface composition, like Scala with traits or true delegation via the manifold project[1] for Java. But that's missing as well e.g., does not inherently fix the Self problem, etc.
Considering Go's initial goal, which was IIRC a better systems language, then yeah, sure it's an improved C. But now that Go is routinely compared with Java/Kotlin and friends, I personally don't see it, particularly wrt the type system, to be taken seriously as a Java contender. Shrug.
1. https://github.com/manifold-systems/manifold/blob/master/man...