Remember that this is very subjective! Every family is different. Also, I don’t think a child needs to never ever ever read a book that is twaddle, but a steady diet of it is not good. I think of books as food for our mind and spirit. Some things we should be consuming often and regularly, other things are ok for the occasional consumption but you could make better (healthier) choices that taste just as good or better.
Some that come to mind:
Captain Underpants, Diary of a Wimpy Kid, books based off cartoon/movie characters like Star Wars/My Little Pony/Lego, Rainbow Magic. Much of teen fiction and adult fiction/romance is twaddle.
I don’t adore Magic Tree House books, so to me they fall in twaddle, BUT they are a perfect stepping stone for a beginning reader to have their own chapter book. That means there is a time and place for them at my house.