First, I think that it doesn't matter whether I or any other poster could eat a roast chicken every day for a decade and never get sick of it. The OP did get sick of it. And, I don't blame her. It's more than once per week. That's a lot.
I think the disconnect here is that if I was bringing someone meals because I wanted to be helpful and save them time and energy in cooking, then I would want to know that my intentions were not actually being met. Just because someone doesn't want to eat the same thing once or twice a week, doesn't mean that they don't love the giver. They just don't want that thing any more. And, if the recipient still wanted meals (just not that particular meal) then I would want them to tell me so. I don't see what's so bad about the recipient saying, "I don't want any more chicken, but I could use some pasta." Or even, "I don't want any more chicken."
I don't see why the recipient should say, "I don't need anymore meals" when it's not the truth. I don't understand why it is better to flat out lie and say that you're back to cooking when you aren't. If someone's feelings are so delicate that they can't stand the thought that someone doesn't want to eat a store-bought rotisserie chicken once to twice a week, then I don't know what to say about that. It's not like they were turning down a gourmet meal that the ILs worked and agonized over. It's about the same effort as going to a McDonalds or Burger King and (around here anyway) less expensive than a pizza.
I'm talking about a close enough relationship here and when the meals are being given multiple times, not a one-time church group or something.