It's definitely frustrating to have so many delays with a service we have to pay for, only for uscis to then just sit on the case for years until you pay for citizenship or they decide it's finally taking up too much desk space.
seeing other people getting RFEs on cases from 2+ years ago for things they submitted at the time because the evidence provided is out of date (or worse, lost) is frustrating too - there seems to have been a fair bit of that lately.