that’s a tough sale to the product team
Sounds like you're not the boss enough!
I agree Rust has a pretty steep learning curve so it's definitely reasonable to worry about people learning it, especially existing employees. Though I don't really buy the "easier to hire people" argument. There are plenty of Rust developers actively looking for Rust jobs, so I suspect you get fewer candidates but the ones you do get are higher quality and more interested.
But anyway I don't think that argument holds for Deno. Typescript is in the same difficulty league as Python. Anyone that knows Python should be able to transition easily.