Apparently there appears to be a great deal of variation in the food quality of different McD's franchisees. Perhaps that's part of their problem - too much variation in food quality amongst franchisees.
One of the things people used to say they liked about McDonalds and what put them on the map really, was people would say they could go to any McDonalds and the Big Mac will be the same no matter where they go. I rarely go there, but I've noticed it is still consistent, but the problem is it is consistent with how it was 30 years ago when there was little competition and expectations were lower. They stayed consistent, everyone else kept improving.
Look at a Big Mac compared to a Wendy's cheeseburger. (purposefully searched for images of the real burger customers get versus stylized marketing images)
..and for good measure, the BK Texas Whopper.
...and one more comparison, the choice of going local. My favorite found just in East Texas. The burger isn't small, the onion rings are just giant. The burger is probably twice the size of a Whopper.
McDonalds is just falling behind by thinking they can keep doing what they've always done with everything else changing.
