If you hang around certain spaces of the internet (here, Reddit, etc), any sufficiently popular post about a Rust-related project is bound to accrue some comments along the lines of "Rust is actually not that great", "rewriting is bound to gain new bugs that won't be caught", "the borrow checker is practically byzantine and not worth the trouble", "C is perfectly adequate", "more advanced type systems are less useful than writing more tests", etc. I would even say that comments of this nature constituted a good chunk of the discussion around the US government's C-to-Rust initiative (a very popular post with a lot of comments).

It's often framed as useless monkey business, rewriting working software to produce a copy of it but in another language, for questionable benefits.

I'd say that rewriting anything in any language (even in the same language) would remove large amounts of cruft, and add long-missing neat things that are easier to add when you build from scratch, and with a good understanding which the original authors lacked. Often it also can afford using a better architecture, see rg vs grep: grep has many brilliant technical solutions, but making it multithreaded would be a major rewrite anyway.

Along with everything else mentioned, there is a certain group of people who consider the language “woke”. Usually that’s not the critique you see on HN, but be wary of it.