I think TypeScript, Scala, Kotlin, C#, and various others I forget now proved that these things weren't a fad and could yield significant gains in productivity and code correctness.
Had Rob Pike been more forward looking (or hired Anders Hejlsberg or Guy Steele to design the language) or dipped further into the PL research, he might have been so bold himself. I don't think anyone can fault him for it, these were niche and minority views in 2010 and may not even be in the majority today.
I think at the same time, we see what happens when a new language has large corporate backing in more recent years. Swift more closely resembles Rust than Go in terms of its type system.