Surely that gap has been filled for at least a decade, even if only by Rust itself?
Moreover, I am not sure that serves as an explanation as it shows up in the strangest places. As you mention Go: Visit any discussion about Go and you'll find some arbitrary comment about Rust, even though, as you point out, they don't even exist in the same niche; being different tools for different jobs.
> Go was originally pitched as a C or C++ replacement
It was originally imagined that it would replace C++ for network servers at Google. The servers part was made abundantly clear. In fact, the team behind it expressed quite a lot of surprise that it eventually found a home doing other things as well.
> you don't see Go ported to microcontrollers for instance.
You don't? https://tinygo.org