There are enough choices that offer Python's productivity alongside JIT/AOT options, better supported from the community than PyPy.
As for the C, C++, Fortran libraries with Python bindings, any language with FFI can call into them as well.
I would say, Python's adoption while lacking performance is what is now building pressure to avoid specific Python communities to leave Python and migrate into one of those ecosystems in search of a better mix of productivity/performance, without being forced to use two languages.
Ooh, a Clojure .NET implementation? This is news to me. From a quick look at the website, it looks really good... but how is it in practice? One of the major advantages of F Sharp's .NET integration is that it's developed by Microsoft, as of course they pretty much created the ecosystem from scratch.
But it is being continuously kept up to date by Cognitect, along with active development on a clojure-clr-next version. Maybe it has a bigger population of non public users.
Also: here's another implementation of Clojure on CLR, "Morgan And Grand Iron Clojure Compiler": https://github.com/nasser/magic (see also http://nas.sr/magic/) of which there's a great cmpiler implementation talk (at Clojure/North) somewhere on Youtube.
As for the C, C++, Fortran libraries with Python bindings, any language with FFI can call into them as well.
I would say, Python's adoption while lacking performance is what is now building pressure to avoid specific Python communities to leave Python and migrate into one of those ecosystems in search of a better mix of productivity/performance, without being forced to use two languages.