Don't like the noodles in casseroles? There are a few I don't for because they are really salty from the canned ingredients.
With lasagna, it's a combination of things that are either bland, or that I just don't like. Probably, if I came across a version w/o ricotta or parmesan, and with some spices to liven up the blandness of the tomato and pasta, I might like it. On an airplane, of all places, I had lasagna w/ pepperoni slices on top, and it's the best lasagna I've ever had. Then again, I was about 12 at the time, so pepperoni was my favorite food.
I can't say exactly what it is about casserole. My wife makes a hash brown casserole that's good, and I like strata, if that counts.