Earlier quoted context omitted.
Does anyone know what might have caused this recent downturn in Apple's software quality?
According to HN threads within the lifetime of any given MacOS release, the last acceptable MacOS was System 8. I'm running a 6-year old MB Pro, updated within the first week of every releases' public beta availability, never reinstalled. I use sudo far too liberally to be good for system health, including (as long as it was possible) deleting all sorts of files in /System, /private, etc. when I run out of space and…
Good luck with that.