The best BLASes (BLIS, openBLAS, and MKL) have lots of C nowadays. IMO it is actually one of their weird cases where C makes more sense: you are mostly tuning GEMM and TRSM, so you can actually throw an unlimited amount of expert C coder effort at them.
But most of the ecosystem other than BLAS doesn’t share this property.
Other than the original reference implementation, you would not find any other fortran version of BLAS anymore. And nobody links to the reference for performance code. All written in either close to metal C with SIMD etc. or straight in assembly altogether. LAPACK is mostly fortran but there are also libraries slowly rewriting those in Rust/Julia and C.
Many high performance numerical computing libraries are “using FORTRAN” in the sense that they’re linking binaries compiled from FORTRAN for numerical linear algebra functionality. Cf BLAS (Basic Linear Algebra Subprograms).