My sense after the fact (I wasn't there and could only see the published stuff) is that EFL couldn't compete with the f77 (later f2c) compiler, which came out at about the same time.  Because the EFL compiler parses the whole language, unlike Ratfor, it can't cope with extensions to Fortran 66+, so it is stuck in the deep past.  Ratfor "does not know [much] Fortran", so if you want to use some new-style declarations or '77-or-later `format' specifiers in Ratfor code, you're cool.  (Although by now Fortran probably does everything Ratfor does, although in a much less C-ish way.)