I don't get the 'limited appeal' and 'ooh she's not a trained chef' arguments TBH.
When I was growing up I remember devouring Claudia Roden's books about Middle Eastern Food, not because I'm Jewish, but because she wove together interesting anecdotes about food history and cultural history with recipes you could cook in a home kitchen. They were absolutely not cheffy - and that was the point. She wrote about the big fancy traditions of palace cooks and so on, but her actual recipes were quite obviously intended to introduce British cooks to new ideas and ingredients quite gently.
A whole host of people have done similar with other religions and cuisines and I love reading that sort of cookbook. I would pick up a book about cooking for Ramadan and Eid because I would hope it'd delve into the traditions around the food as well as the food itself. It's not because I'm Muslim and need 10 ways to manage halal lamb!
I also think there is a certain faux-naïveté in people saying that Nadiya should have predicted better how such a cookbook might sell or be marketed. I sincerely doubt she does all of this on her own kitchen table then rocks up to her agent and her publisher saying 'here's the finished project, off you go'. They will have had a discussion about it all.
I would imagine she is speaking out about the attitudes she is encountering, not to 'whinge' or, as a PP suggested, because she doesn't understand that it might look negative to potential employers, but because she has a platform and she wants to use it to make things better for other people in her situation.