Fortran has never been used seriously for systems programming. It got text processing capabilities and a ton of other stuff, but we do not see operating systems or web servers written in Fortran.

And C got the floating point operations B did not have, and was actually used for lots of numerical work for a while (and it still is, up to some point), but nobody was totally happy with it so we got C++, new Fortran versions, Python, now Julia... Although it always is an option due to the availability and quality of C compilers, I would not say that C succeeded in becoming the language of choice for scientific computing.

Of course, this does not mean that C or Fortran are failures.