Most of the common C dependencies were implemented in Go before its public release - https://golang.org/doc/go1. These implementors are exactly the "better-equipped" original authors to which the blog post was referring.
Most programmers are programmers for hire, and it would be a waste of everyone's time to re-implement (for example) libdispatch in Rust. If someone wants to write it on their own time for their own edification and no other purpose, fine -- but half-assed internal implementations of common functionality are a significant drag on the lives of other working programmers.
All of this has absolutely, truly, nothing to do with rewriting something in Rust. You could also rewrite the same library again in C and have the exact same conundrum.
Also, people build dependencies on effectively “hobby” projects all the time. Open source in particular works well this way because the dependents have a good reason to contribute back; the users become stakeholders and contributors. The same may not be true of internal software, but again, this has little to do with the concept of rewriting something in Rust.
This is really diverging into a discussion that has nothing to do with the original paragraph I addressed.
Most programmers are programmers for hire, and it would be a waste of everyone's time to re-implement (for example) libdispatch in Rust. If someone wants to write it on their own time for their own edification and no other purpose, fine -- but half-assed internal implementations of common functionality are a significant drag on the lives of other working programmers.