*IF* the IRS accepts paper documents, the system is how it has to be.
The article is _VERY_ misleading with "... staff opening envelopes and typing in details by hand from the submitted forms rather than using automation and OCR". While technically true, in the late 1990's IRS "Service Centers" tried to have employees use OCR on small business documents and most individual forms, it was catastrophic. The results were that it took longer to align and fix OCR mistakes than it did to input these forms by hand on custom made keyboards (about 3x longer). Those were primarily business forms processed at service centers and the individual forms are essentially impossible to OCR if filled by hand so, sometimes 3x longer turned into 3 whole shifts longer (1 full day).
The IRS does/did have a large OCR process that utilizes primarily a custom C backend with embedded CSQL Although this system was/is being phased out for a system I do not know, it was the system used during the highest volume (80's to early 2000's).
When you have ~350 _MILLION_ people who basically file their taxes and can do so with paper, you're going to have to deal with MASSIVE amounts of paper with erratic pen/pencil/crayon/shit marks all over them. OCR will never speed up work but, stopping paper submissions would (doubt that will ever happen).
BTW, it's legal to pay your taxes in pennies, so the IRS also has a system in place to count say $100,000 worth of pennies (it's large sliding trays... but systems like these exists).