If you asked the general public about the best published novels you would get a different answer than if you asked avid literary readers and a different answer if you asked the publishers and gatekeepers of old. It's part of the discussion. I read Ulysses, it is a great book, a great study in metafiction, a great idea. It is also a difficult read for sure. I wouldn't place it on my list of great novels I think people should read, but I understand why it exists on these lists of books. Did I understand all of it when I was reading it? Definitely not. Did I get a lot out of the book. Yes. Were some parts irritating? Yes. Were some parts funny and thought-provoking? Yes.
For me Joyce is a maddening writer because he can be long-winded and quite boring, but then he writes a couple of lines that for me are pure brilliance and I forgive him for the rest.
Well, maybe not all the rest, but large portions of it.