Go is a kitchen full of dull knives. It is good for layers of communication where you call other microservices to perform the heavy lifting, but not much else.
In most cases it doesn't have "poor" performance and if you're going for optimal performance you are almost never going to be using generic data structures anyways because there's almost always type specific optimizations that can be done.
The intended use case is, and always has been, decently performing type safe data structures and Go generics are sufficient in most cases for that. Go is never going to be a functional programming language.
I imagine there's a rationale for not implementing generics this way, like keeping binaries small, but it seems like a weird tradeoff considering it increases overall memory consumption and decreases performance quite a lot...