First off, every band is overrated by fanboys, and underrated by people who hate them. It's a fact of life. That's why, at least for me, I don't pay attention to what pretty much anyone says about bands until I've heard them myself. There's good and bad in all music, and you're just supposed to listen to what appeals to you and not listen to everything else. Is it really that complicated?
No, you're not alone in not liking Radiohead, a lot of people don't. But why the hell does it matter? That's the case for every band, and the only reason this is an issue at all is because they're "popular" and people "like them". If you don't, you don't, you shouldn't feel like you need to justify that. I think the Rolling Stones (aside from a few songs) were shit, I can't listen to most black metal (or most other kinds of metal, for that matter, especially of Nordic origin) because it ALL SOUNDS THE SAME, most "ambient music" isn't really music, and I think that most indie is awful, and just like any other genre, you have to dig through fifty albums of crap to find one good record. A lot of people would crucify me for those statements, but I couldn't care less.
If you're really looking for reasons people like them, I'm hesitant to say any because people who don't like a band always find a way to contradict anything you have to say. But I'll put myself out there anyway. I like Radiohead because they're interesting. The progression of different styles and new directions from their early stuff 'til now is awesome. I'm proud of the guys for not "finding a sound and sticking to it," because that's the way most creative decay comes about. I think most of their tunes are catchy and easy to listen to, but with enough musical and lyrical depth to hold my interest after a number of hearings. They're pop-y, but not TOO much so. Kid A and Amnesiac (both of which I'm still in love with after years of listening) are especially cool because they compliment and respond to each other so much. They make concept albums and push their own creative boundaries, but aren't too high and mighty to think they write the best stuff ever to come out of your speaker box. But the most important thing is, it just agrees with me.
There, that enough for you?