You're completely right, the argument is a red herring. People did not move away from cooperative multitasking for operating systems because it solved every "ru

You're completely right, the argument is a red herring. People did not move away from cooperative multitasking for operating systems because it solved every "run-away usage of resource" problem for all time. They did it specifically because, as you note, it makes incredibly simple application-level errors, whether they are design-level (UI thread blocked) or simple errors (accidental infinite loop) totally devastating to the entire state of the system. This is pretty bad whenever your system is designed to run arbitrary computer programs.