Well, as far as I go, I definitely don't believe that Harry Potter is poorly written. Are you sure you're not confusing them with the Twilight books? Just kidding...sort of.
I guess the reason why everyone is "so obsessed" with Harry Potter is because they personally like them. We're all entitled to our own opinions. That being said, if you don't find the series appealing, people angrily replying to this telling you why they are awesome isn't going to give you a good answer. I find them appealing because it's a wonderful coming of age epic series that is expertly written and incredibly imaginative; her characters are so well fleshed out and I enjoy the plot.
[And I love the fact that someone above me quoted Bob Dylan. Dylan is a great love of mine, but he also said, "I am the spokesperson for my generation" and then repeatedly denied it in interviews. If you want to talk about a man doing what's popular, albeit doing it well, Dylan is the biggest hypocrite alive.]