meanwhile, back in the coporate world
FTP chugs along feeding data from unices, Windows, whatever relics like VMS lying around to the organisations mainframe. Not something one uses outside of a couple of firewalls, but I can think of multiple government sites where FTP gets data from A to B quietly and reliably if one scripts decent post transfer log analysis. FTP use is fading as ssh takes over. Somehow I do not see Kermit coming back either.
As for hard to use argument, BH. Download WS-FTP or equivalent, read instructions, configure, compile and install or download existing compiled package if lazy and trusting. It is simple to set up an anonymous FTP server. Simpler than NFS even. Throughput I find better than http. Don't know about caching. Given the size of the files I transferred or their contents, non-caching is desirable. Perhaps this is another sign of the dumbing down of IT as the lowest common denominator consumer experience sets standards.
Agreed ftp is not secure. Once can add a little security by using Franceso Rosales shell compiler or using the equivalent in ksh93 that hides the account details from causal snooping.
Given the lack of use, decommissioning FTP is logical for Debian. Whether it will fade away or become another "Death of COBOL predicted" meme is debatable. Meanwhile, back to Devuan install