Yeah I think people understate how large of an impact this had.
My immediate reaction to that was the "jig is up"--I argued with friends that Twitters functionality would remain intact, there'd be no major outages, etc and they couldn't understand how that'd be possible.
Many if not most engineers are working on things 2-5 years out, not keeping services running.
i think the total reduction was about 2/3 if memory serves? so 1 in 3 is that number you'd be looking at for "actually useful". heavy air quotes on that.