You could bolster your claim that it's a canard by linking to several other US government-built websites doing as complex a job as filing taxes that are convenient and easy to use.
I mean their free file fillable forms is fine. I have used it for a number of years now and it is perfectly functional. Everyone points to how easy the big wigs are but I found the only difference is some slightly nicer phrasing and making it harder to miss EIC and such.
If they automatically filled in the information they had and fleshed out the calculator bits (like not making you use a tax table by hand) it would be a fine tool.
the US digital "corps" (not sure what they're called) is widely regarded, helping the VA if not healthcare.gov directly. people are even giving up vaunted Private Sector jobs to join them.
i have a feeling, if not defeated by anti government types they could do the job.
I certainly could -- but why should I hold myself to a higher standard of evidence than do you yourself? Also, you have moved the goalposts by now singling out the U.S. government.