From a non-US perspective, hearing/reading about how tax returns work there is some kind of crazy Byzantine nightmare.

In Aus, I file it through a free, online government portal.

Most of my stuff is pre-filled: personal income, social support payments, bank interest, dividends/managed fund distributions, etc. Previous years' deductions are rolled over with relevant data pre-filled, which then prompts me to fill in the blanks through a series of steps. There's relevant depreciation calculators for various work-related purchases (laptops, cars, etc.) that all align with the tax office's advice around depreciation durations and rates.

All of this is known because most (i.e. bigger) companies are required to hold your tax file number and report on salaries paid, pension contributions and withheld tax. If you don't give them your TFN, they tax you at the highest rate and then you will get the difference back upon filing a return. If it's not pre-filled, you get your data on a payment summary at the end of financial year and just put it in manually - again, it guides you through this. For a standard white collar worker, because my employer knows how much they're paying me, they can accurately estimate the total income I'll get over a year and thus accurately withhold tax. This means my tax return is generally pretty much a wash until deductions or extra income starts moving it, but that's only a couple of percent usually.

For stuff like bank interest, you can choose to give them your TFN, or you can just enter it manually and the return process will calculate it out in the process.

You can of course delete and re-enter any of the pre-filled information if it's somehow wrong. You're not under any obligation to use the pre-filled data.

The upshot of this is that for the overwhelming majority of people who don't have complicated tax arrangements, it's entirely possible to do it all by yourself, for free. You are of course always able to have an accountant do it for you (the system has processes for them to file a return on your behalf). The underlying principle is that everyone can in theory do their own tax return no matter how complex, though of course that means reading up on a lot of the tax code (the tax office tries to provide relevant examples of how the various rules work). But if you're a standard white collar employee working a 9-5 with some basic investments (e.g. your pension and a small stock portfolio, maybe an investment property if you want to throw in some non-prefilled complexity, and you've got some basic deductions such as through donations and work expenses) it's going to be pretty easy to do with a few hours' research, max.

Hell, I think I could still even use the paper forms for this all, but why?

I suspect that US readers will, on average, baulk at this level of government oversight and the idea that big brother sees all of your income, etc. but the reality is it's still possible to do cash-in-hand jobs and lie on your return so if you're in for a penny re: committing tax fraud, you may as well be in for a pound. Besides, the main way of doing the dodgy on your tax return in Australia is via declaring deductions that you're not fully entitled to (e.g. 100% deduction of your mixed work/personal phone, rather than just the pro-rata amount of use for work) and hoping that you don't stand out too much on a statistical analysis to be audited.