This is because what you call "systems" is not the "systems" that the lack of GC would benefit from. For all intents and purposes Kubernetes could be written in Python or any other general purpose programming language (and for example OpenStack is in fact written in Python).
On the other hand, systems like "writing an operating system kernel" or "running on a microcontroller" are things where GC might indeed be problematic and/or impractical.
Also, writing self-referential data-structures is very difficult in Rust (but not impossible) due to the type system. I suspect that a lot of developers who just want to get work done get turned off by fighting with the typechecker, and choose GoLang instead.
And also: GoLang is a very accessible language, that can be mastered in a couple of days.
Not really true (at least, not nearly to the same extent) since Pin<> was stabilized. I suppose that only serves to prove your point about Rust still being "in research phase", though!
Other things like the situation with async/coroutines is still it great in rust.
Go is, syntactically, a much simpler language than rust.
It all depends on what you need, what you want, and where then community around it is (e.g. Docker came first and was written in Go).
You'd be surprised.
Kubernetes may as well have been written in Python. It's mainly IO bound, so the benefits of compilation as opposed to running on an interpreted VM (like Python) aren't that big.
Now I am not arguing one way or another. People can just have opinions or they can just write software or they can do both.