Similarly, my company are 4 years into a rewrite of a cobol mainframe system much simpler than Social Security. Which was going to "take a year" there's at least 5 years left.
I know the UK benefits system took well over 12 years to build with an programming workforce of over 2000 and I imagine it's simpler having to support a population one fifth the size of the US.
Whilst the home office are generally appalling, this is particularly concerning! The reduction in number of successful asylum seekers from Afghanistan of all places, where the British spent over a decade blowing up and then to abandon those who worked with us there is vile!