[kjs3]

Yes...Fortran at least has changed a lot since inception. There's been Fortran 90, 95, 2003, 2008 & 2018 standards since to keep up with the various industry fads of the time (You want OO Fortran? Sure thing.). You can get a good overview of Fortran features from inception through the 2008 standard in the paper "The Seven Ages of Fortran" by Michael Metcalf or on the Fortran wiki (https://fortranwiki.org/fortran/show/Standards).

[dspillett]

Does a lot of that extra pool of features get used in production (relative to more "legacy" code) as seen with many reengineering JS projects regularly, it is the Fortran user base more conservative? I might expect the latter, but this is just a gut guess.

[kjs3]

I'm not doing much work with Fortran-using communities these days, so this is an opinion only, and probably out of date in various ways.

Yes, developers are using the new features. Most code I touched was regularly using up to 2003 features, with later stuff dependent on other factors (solid compiler support across different compilers being a big one). However, most Fortran programs are going to be fleshed out with components taken from the vast collections of well debugged and tested libraries available, many of which are still F77, and probably will stay that way. Fortran is more 'conservative' in the sense that there's not much compulsion to rewrite working code in the name of 'refactoring' or whatever. Adoption of new features is more 'I'm going to use a select set of things that will make my life appreciably easier' rather than 'everyone on board with all the latest shiny things'.