The company last year had 660 cancellations and 11000 flights were delayed.
The statistic means nothing unless you know what was the total number of number of flights GF did. If we assume GF did 100 flights per day (and probably more in peak summer), then this means a total of 30% of all flights were delayed. A bit on the high side, but not uncommon. I am not sure if it is even possible with a fleet as old as the one GF has do any better.