By "poorly written" I don't mean shortcoming in terms of literary merits. That's a different discussion. What I mean is a story that doesn't move YOU. (It might've moved other people, but it left YOU cold).
When you read a book that you set aside in disgust or disappointment, or you watch a movie that you pause and can't finish watching (or walk out of the movie theater), I invite you to take some distance from it (a day or two), then come back to it and try it again and analyze why is it that you didn't care for it.
Better yet, make it a habit of reading or watching something that doesn't move you regularly, like once a month or so. Yes, add it to your writing routine as part of your education.
For me recently this was the experience of reading The Da Vinci Code then attempting to watch the movie. While the book was fast-paced and wouldn't let me off the hook (except some lengthy historical descriptions that did slow me down a bit), the movie didn't follow the 12 Columns structure, watering it down in Column 1 right away by not making it clear who the Villain is (in the book we have a clear Villain by Proxy) and who the Hero is and what the goal of the movie is, so I couldn't actually watch it past the 30-minute mark. I'll step away and then go back and attempt to watch it again, to nail down exactly where it didn't work and why, and learn not to do it in my own writing.