Re: An age ago. Or two.
"it didn't trigger a sea change in re-architecting software."
Actually, yes. It did. For one thing, it triggered the formation of CERT by DARPA.
By the late '80s, most OSes might have contained exploitable holes, however those exploits were no longer accessible outside the corporate network. (Assumes adequate capability in charge of the firewall, of course.)
The corporate world consolidating on Windows just made life easier from the crackers perspective ... Monocultures in computing are just as bad as they are in farming, and for the same reasons.
Contrary to popular belief, Internet access was widespread before 1990.