Also javascript and typescript are not well suited for compilers and dev tooling.
It shouldn't be seen as a negative that Deno is using rust in places where it really shines, which is a totally different use case than what deno is typically used for.
Developer tooling is not complicated and there is plenty of existing tools written in JavaScript, so it seems weird when they rule out there own language as not good enough. It should make anyone think twice before using Deno server side if it is not good enough for themselves.
Specifically, Typescript has a larger talent pool of experts to hire from. Although, I do hope that changes for Rust over the next 5 years.