they seem to say the old code is hard to maintain
But I just keep thinking that generic plain text ftp which is probably 99% of ftp sites out there hasn't changed much at all in probably 20+ years so there shouldn't really be much of anything to maintain.
I don't use ftp too often, and generally when I do I use ncftp.
Checking ncftp's changelog they released version 3.0.0 in March 2000, now they are at 3.2.6(from late 2016), for a dedicated ftp client just a point as to how little ftp has changed over the past 20 years.