It's not just you, at least I partly agree.
Although I personally really enjoy the films, I've always had my doubt as the wether they would be enjoyable (or even make sense) to someone who wasn't familiar with the stories beforehand.
-I think maybe Going Postal is a bit better in that respect than the first two. Although I'm sure the golems will confuse many, as it isn't really explained in the story what they are. (This was done very well in Feet of Clay, but if you haven't read that...). Like you, I'm not sure the films make anybody want to read the books if they don't already.
That being said, I do want more of them to be made, because I think it's fun to see the books on screen, and see how other people (directors, set designers and actors) imagine the Discworld. It's never going to be exactly how I (or any other one person) imagine it, but that's OK with me.