But even then you are still depending on others to catch the bugs for you and it doesn't scale: if everybody did the cooldown thing you'd be right back where you started.
(This may end up not being true, in which case a lot of people are paying security vendors a lot of money to essentially regurgitate vulnerability feeds at them.)
Until no-one does, for a week. To stretch the original metaphor, instead of an overgrazed pasture, we grow a communally untended thicket which may or may not have snakes when we finally enter.
The "until no one does" is not something that can happen in something like npm ecosystem, or even among the specific user of "left-pad".