He spent decades at Bell Labs. He was also, IIRC, in his seventies.

So a more charitable interpretation would be that most of his colleagues are in their 20s and just out of school with a CS degree. He doesn't think they can (productively) use the languages the cutting-edge PL researchers generate.

Like I said, he clearly doesn’t think very highly of them. A fresh college graduate could learn how to use sum types in a day or two.

Sure they could. Sum types aren't in go, not because fresh grads can't learn how to use sum types, but because they couldn't see a clean way to add it to go and have it fit with the other stuff they were putting in go, which they thought was more important.

But trying to get new grads to use Haskell on the scale of a 10 million line code base, and have them not make a mess of it? That's the kind of thing he didn't trust the new grads with.

Just a clarification (that doesn't really change the point), he was in his early fifties when Go was first released

> They’re typically, fairly young, fresh out of school

these same lowly colleagues were also incapable of wiping their asses at one point in their life but over the years and skidmarks, they all mastered that beautiful language and now make heated bidet money.