Leaving aside whether it makes sense to call something "useless" that was actually used in the wild, the original article specifically mentions (twice) that the

Leaving aside whether it makes sense to call something "useless" that was actually used in the wild, the original article specifically mentions (twice) that the Firefox RCE 0-day was also sandboxed and also only managed to escape thanks to another 0-day. (And I'm actually a Chrome user, for now.)