My point was more that there wasn't really a need to reinvent this wheel in terms of everything else. Not only is there a battle tested production system serving millions already, big chunks of it are in a MIT github repo.
That said I understand why the IRS doesn't just want to copy another country's. Not invented here and all that. But from the various countries systems I've used...the UK one is fantastic. Not just tax...same pretty clean UI and design across all the big gov sites.