Earlier quoted context omitted.
Sorry to bring up this yet-another-generics-ranty-thing, but actually point 4 is a typical issue that can be nicely solved with generics, by defining a function that works on every type that implements Foo. In this way you can directly pass a slice of Foo to the function and achieve type safety at the same time. As stated by the author, there's a demand for manually constructing an interface-slice in Go, and this sho…
That's a different criticism. That's the "Go Needs Generics" issue. I don't disagree with it, but I also agree that there hasn't been any good solutions proposed for generics that meet the requirements that are at the core of Go: namely, performance of the compiled program, performance of the compiler, and performance of the developer.
As for the core features of Go you mentioned, sorry again for my cynical wording, but I think they are a bit dishonest.
They stress on the performance of the program, yet being slower than C/C++ due to the usage of GC and dynamic dispatch all the time. It was even regressed in Go 1.5[1], because the new GC prefers latency to performance. So, they traded performance for something considered more important.
How about the performance of the compiler? Well, the speed of the Go 1.5 compiler is ~10% worse than the previous one, because they rewrote the compiler in Go (it was previously in C, for those who didn't know yet). Why did they do so? Because it has advantages: reduces the barrier to contribute to the compiler, improves the code quality, etc.. Yet they traded performance for something they consider to be important.
And the performance of the developer... While Go is not very terrible at developer experiences, it isn't very good either. Embracing simplicity led to lack of expressiveness, a typical example being generics. While this isn't entirely a bad thing, it is, again, a trade-off.
So they make trade-offs all the time. Then why are generics not considered to be good enough to make a trade-off? Because they think so. It is their opinion, sure, but claiming generics are impossible because performance isn't very convincing to me.
[1] http://yokohummer7.github.io/blog/2015/09/01/go-1.5-regressi...