Not so much sucks as just exceptionally mediocre.
Popeyes and Culvers are both much better. Even KFC is better.
Culvers is great overall. It depends who they have working there that knocks a couple of them out for me. Some places the grill folks dont clean the grill enough between batches and you get a lot of fried grease / acrylic crap instead of a tasty burger with some char.