With that said, I am absolutely "pro" automatic filing.
The IRS operates at scale.
I disagree that the IRS has an incentive to maximize taxes. They have an incentive not to lose time with disputes.
But even if you don't trust them, so what? You can still check the numbers yourself, and file your own if you disagree.
Prior to WW-II, everybody had to file quarterly income tax payments. It was during WW-II that withholding became a thing (maybe something to do with increasing monetary flow towards the government or something). It remained a thing afterwards.
Because of the withholding, most people are unaware of exactly how much they are actually paying in taxes, especially given the "windfall" every year of refunds. "Woo hoo! Gubment gave me money!" and all that.
It basically does everything that an individual could need to do, although you can go to an accountant if you want (if you can't be bothered, or have particularly complex things you need advice on).