Yeah I wouldn't call it keys to the castle. But you can confirm your competitor has a penalty, and if they do run a negative SEO campaign (bad links) and to make it harder for them to get out of
It doesn't feed back into the ML directly, according to Google. Instead they use it to evaluate changes to search algorithms. If they get an increase in thumbs up back from the Quality Raters then their changes were positive. If not, they figure out why.