Re the selling point: You're underestimating the importance of a conceptually simple language. If you put a new developer on a project in any other language that he has never used before, he will need at least a week to get up to speed. With Go, I had colleagues sending me pull requests with real, useful feature additions to my Go programs within 1-2 days of them installing the compiler.
Sure, but maybe you're overestimating the complexity of Generics (on the programmers, not the implementation of the compiler side)?
What makes you think those same programmers could not grok them? They could grok CSP (channels etc), implicit interfaces, pointers, reflection, unsafe pointer work, and closures, but suddenly Generics are too much? Seems rather arbitrary -- especially since the language already has generic functions.
It's also the matter of initial familiarity (productive in a few days) with eventual expressiveness and power (how much more productive in a few months and more)?
Because your argument seems to me like saying Go is Nano: one can start editing immediately.
Sure, but Vim/Emacs are worth the investment in learning them, even if one feels lost for a little while when starting with them.
The selling point of Go for most people is rather: hey, a language with GC (easy to manage memory) AND nice parallel/concurrency story AND static builds AND faster than my dynamic language I use.
I don't think "it lacks generics" comes into play much as any kind of benefit.