I'm sorry, I respectfully disagree on the "not enough" :-)

I think it is a matter of choice of audience. If you want pure functional languages, there are plenty that will rock your boat (Haskell, OCaml ...).

But, to my mind, I see Rust as a somewhat "modernised" C/C++ with, like Python, the most interesting and accessible parts of FP backed in. It is a balance and it is fragile. So, as I said, I hope that Rust will keep that fine line.

All that said, it only is my opinion, I might be wrong and the wider audience might be ready for "harder" FP. But I doubt it.