All I can add is that when dealing with IRS personnel, be kind. They are very aware of the situation in which everyone finds themselves. "The agency faces staff shortages, with fewer than 15,000 workers handling 240 million calls last year. Its workforce is the same size it was in 1970, with a budget 20 percent lower than it was 10 years ago." And then there's the technology infrastructure, which is an issue all to itself.

A lot of it is done by optical scanning now, but if you have less-than-perfect handwriting or if it's a Tuesday in a month with the letter "R" in it, things... can happen to your paperwork.
https://www.nbcnews.com/business/consumer/get-ready-frustrating-tax-season-warns-irs-historic-backlogs-staff-sho-rcna11834Covid has hit all employers hard, and the prior administrations did some rather strange budgetary things that impacted the USPS and the IRS (among other agencies). So the folks that are on the ground there in the agencies are having to do the best they can with what they've got. I regularly have to work with the VA and whereas pre-Covid responses came within about 72 hours it's now taking three weeks, minimum. That's for priority calls on back-channels.
The Executive proposes budgets, but Congressional politics determines what funding is actually provided. So if you have a burning need to complain to someone "in authority", send a nastygram to your Congressman. It won't do any good, really, but it might make you feel better.
