I agree there's some risk involved here, but the kind of thinking that you should stick to what you know can lead to stagnation. I much prefer the mental model of "capable engineers can pick up any language". Sure, it'll take time to learn these things, but it should not be a blocker.
> capable engineers can pick up any language
Sure, given that they are getting paid for it. How many people will be interested in learning a programming language with insignificant job availability, in addition to contributing for free?
Your argument about stagnation is good, but "capable engineers can pick up any language" is not without costs for the involved developers in terms of time spent learning paradigms, features, bugs, gotchas (like temporary lifetime gotchas in Rust encouraged by the constraints of the borrow checker, still a widespread issue in 2026 https://fasterthanli.me/articles/a-rust-match-made-in-hell ), APIs, libraries, ecosystem, build systems, etc.
They would also have to figure out how to approach distribution, organization, linking, etc.