Team dynamics in large companies can be quite challenging. In addition, whoever made that decision might become responsible for project delays, inability to hire, people writing bad code, destroying work-life balance etc. And not just you, everyone up the chain will get blamed for choosing a programming language with a near-zero market share.

Generally large companies and enterprises are resistant to change, and my advice will be to just ask for enough room to get the project executed somewhat within budget and schedule.

At Olo, which is primarily a C# shop, people have been excited to learn F#, and able to pick it up on an as needed basis. We are pretty large and it has been fine. It helps quite a bit that it is a different language but part of the same ecosystem. It is quite a bit easier to manage than it would be adding say, Go, or Rust or something into the company, with entirely new tooling and libraries. for instance a visual studio solution can contain C# and F# projects, and they can refer to each other.

Your original point was about inability to recruit developers. That is why I asked. From my experience it was never a problem for seasoned developer to get a grip on new language barring few very exotic cases. I completely understand other factors in enterprise.