The so what was meant at the futility of using goals to measure performance. A team could lose 5-0 but have played quite well and very evenly matched in number of chances, possession, etc., just having been unlucky to concede on every shot by their opponent. Of course this performance from Granada was atrocious, one of the worst that I can remember in recent times, but it's quite clearly an outlier.
In the end this doesn't change much in terms of competitiveness, whether Granada had played similarly bad and only lost 3-0 would that have made it somehow a more competitive match? In those terms there have been plenty of worse teams in the PL in the previous decade... Sunderland 05/06, Watford, Wolves, Wigan, and the worst of all, Derby in 07/08.