It's hard to explain if you aren't someone who knows the books (and the books behind those books, e.g. the Silmarillion, the Lost Tales, etc...) intimately. I pretty much read through the whole bunch about once a year. I have the same reaction to any rendition of Dune so far as well, though even more so, making me almost puke honestly. LOTRs wasn't that bad, but it just seems to seriously lack something the books have. Of course it has lots of eye candy, and people can enjoy it on that level easily enough. But it just seemed extremely two dimensional and simplified to me compared to the book.
Ultimately, I think it's inevitable. They have to pander to some degree in these kinds of movies because, if they don't bring in a lot of people who haven't read they books, they can't make their money back. So it has to be dumbed down considerably just to be made at all, unless some dying billionaire decides to fund it as a gift to mankind or something. So you get things like Legolas doing Cirque du Elve slides down the trunk of an elephant, and the overly jokey Gimli character, stuff like that. Not that there isn't plenty of humor in the books, but it is usually pretty subtle stuff. The silly scene of Denethor eating like a pig, when in the books he is (despite being destroyed by stress) a very noble person. Too much emphasis on the Aragorn/Arwen thing, which is clearly fundamental to Aragorn's character but hardly present in the books at all, and played up purely for love interest pandering purposes in the movie. Faramir's reaction to Frodo and the ring is completely different in the movies and belittles him I thought. Sauramon's death spike fall from the tower was silly. And, though it would have certainly added time, one of the major points of the books is that the adventure turned the hobbits from basically kids into leaders who will subsequently guide their people forward, and that's really lost when they dumped the majority of the return to Hobbiton. Losing Tom Bombadil is probably the most justifiable change I guess.
I guess for it to be done the way I'd have preferred it, someone would have to give the BBC a couple billion to do it as a 10 part mini-series or something.