... If they have all the information, why are they making me corroborate what they have? ... They already know what I owe, so why bother going through the hoops? The only variables are your deductions, so, just send in your deductions on a form and let them do the math!
The IRS largely know your income...
But they could send you the basics, and then ask if you accept it, or want to add deductible expenses (I think there were earlier posts saying this is what some countries do)...
...if that populates with what they have and all I need to do is a quick stare and compare, it will save me time and mistakes...
I don't think the IRS actually knows your individual info early enough in the tax filing season to be able to create a partial return for you. Payroll tax returns filed throughout the year don't show individual employee SSNs, just an aggregate total for the employer. I'm not sure about other types of withholding, such as from pensions and IRAs, but I assume it's the same (which would explain why the loophole of doing all your withholding via an IRA withdrawal in December works).
The IRS does get W-2s at the same time the taxpayers do, but most 1099s don't have to be filed with them until March 31. Then after the IRS gets all these forms, it takes about 8 weeks before they have it sorted by taxpayer so it can be used to prepare a return. I just tried to pull a wage & income transcript for myself for 2022 and it's not ready yet, so I'd still be waiting if I were relying on the IRS to do my tax return for me.
It seems like if we want the IRS to prepare the income portion of returns, Congress would either have to change a lot of other processes and forms, or change the filing season so it starts in June instead of February.