The New York Times ran an article on this just last week.
appointments at passport agencies across the country remain elusive, and processing time for renewals by mail is lagging by 10 weeks or more
In-person appointments are only available for those traveling within 72 hours, and it has been like that for a couple of decades or so. One person mentioned in the article
mailed [his application] in for renewal and paid for expedited processing, which before the pandemic would have taken up to three weeks. After five weeks, with his passport still processing and his trip departure looming, he began hunting online for an appointment at one of the State Department’s 26 official passport centers and passport agencies, where he could renew in person and get the document in one day. It was much harder than he imagined.
Routine passport service by mail, according to the State Department, can now take up to 18 weeks, compared to six to eight weeks before the pandemic, while expedited service, which costs an additional $60 and took anywhere from a few days to three weeks before Covid-19, can now take up to 12 weeks.
The last time I renewed my passport by mail, it took two weeks even though I did not submit an expedited application. That was 12 years ago, and obviously the probability of that happening now is zero.