FOSS seems to be adopted by most Internet companies, where Swift, C# and .NET are fringe languages.
clang and gcc produce faster code than Visual Studio and are more pleasant to use. IBM is now using clang in its terrible xlc compiler.
Mathematica uses gmp (in (gasp) C!), there's no commercial alternative to gmp or mpfr.
If you are writing apps for iOS or Windows, sure, the cited languages are better. That is quite a narrow field though and I'm not sure how FOSS could enter that field.
