Since Rustaceans are so neurotic about rewriting everything in Rust, I genuinely thought that an article about rewriting Rust (in Rust) had to be a meta-satirical joke.
Well, if you work on security-critical software that's currently written in a memory-unsafe language, I would say that's a good candidate for a Rust rewrite. Likewise if you work on a widely used library that's awkwardly slow because it's written in python.
Which is not exactly the same as wanting everybody to rewrite everything in Rust, but I suppose it's the sort of thing that annoys nineteen999.
There are also a lot of devs rewriting things in Rust for their own entertainment or whatever, which I think is the main source of the "rewrite everything in Rust" meme.
It's a good candidate for a rewrite in a memory-safe language, of which is Rust but one. Some people don't like the Rust syntax, the cargo ecosystem's resemblence to npm, the gulf between what's in stable vs nightly rust (ie. ISO standardization might be nice to consider at this point), personal attacks on experienced C/C++ programmers by well-meaning but junior devs in the Rust community who would be better served (re)writing stuff to prove their point rather than evangelizing so much. Some us also find the sensitivity to any kind of criticism of these aspects a little amusing, so we occasionally poke fun in return.
There are still plenty of constrained environments, architectures not yet supported, a lack of mature libraries for 2D/3D graphics amongst other things, that make Rust not a good fit yet for many projects where C/C++ already works. When Rust gets there and it and it's community matures a bit, we will all cheer. Until then ... we'll just get back to work.
