It's not that it sucks, it is error prone. Completely ignore a knowledge of tax law for a moment. Data has to be copied from one form to another, copied for calculation (whether you do it on paper or with a calculator), copied from one line to another, and finally copied from the form into the government's tax software. Each step produces the potential for error. Properly written software does not have the same potential for error.

I quit doing paper forms ~10 years ago when I missed coping line 12c from form 5678-e to line 34-f of form 9876-k. The hassle of correcting that was enough to make me quit doing taxes by hand.

It takes longer to do my taxes via the web forms than it did by hand (which says just how bad the UI of tax prep is!), but it saves me from human mistakes.

Note that the ISR already has all the information they need to do my taxes for me. They just don't do them.

I can also walk down to the nearby river to launder my clothes and carry back water to prepare food for my family. Instead we use technology to save time and improve our lives. That we continue to allow corrupt businesses to hold us back so a few people can extort/profit is a testament to our failed state.

I've thought about doing that before just to say that I've done it, but it always seemed a bit intimidating. I also have completely illegible handwriting now, so filling anything in by hand is effectively a non-starter.