This post from Larry Kahaner makes me nod in agreement. As a writer who’s still very much learning the craft, I believe it’s a great idea to read not-so-good prose as well as the really excellent stuff.
Don’t waste hours reading something that makes your toes curl – that’d be cruelty to yourself. But spending time analysing the ways in which a piece doesn’t work is useful. The questions should make you think. Why doesn’t it grab me? What is it about the writing that’s irritating? Why don’t I engage with the characters? How does my own writing stand up in comparison?
It’s easy enough to pick apart another’s writing but the real benefit comes from a clear-eyed view of your own efforts. And don’t forget, you too were once at the beginning.