I think there is nothing to prove, I set up my prosody just by reading the documentation -- eventually https://compliance.conversations.im/ is a great tool to see how well you are doing, and which modules are worth uncommenting lines from the initial config file. I have a functional and working server with just a score of 85%.
The only real pain point could be iOS, but it is the platform the one that makes things extra difficult, see for example what happens with browsers (https://en.wikipedia.org/wiki/Firefox_for_iOS)
wrt to old crusty FORTRAN code: scipy is using many of those popular libraries, it is based on them.
wrt to type signatures, many of those ancient FORTRAN libraries are written with implicit interfaces, so bugs are likely to show up. I came to learn this when compared some versions floating around with the patched versions supplied with scipy.
My aim is not to bash, but justify scipy is a solid piece of software, based on known developments, not just a shiny "new" thing.