No, really, I used to feel that way, but I've been using Pandora lately and they've thrown a couple of Dead songs at me that I've found palatable. anything that runs over three minutes gets canned, though.
And I like the shoegazers. heck, I like a lot of derivative stuff. I worship the Strokes, because what they do what they do so well (and what they do, to me, has always been perfect pop, pure and simple). If it's good, it's good, and a lot of that to me comes just from the quality of songwriting even if it's inspired by others. Some original stuff is awful. Case in point: the Fiery Furnaces. Burns my ears. But a lot of bands you mention -- String Cheese Incident, Simple Plan, Styx -- they're not bad because they're based on another. They're bad because they're just not very good. Their songs blow.