I'd say hate is a strong word. I've seen more contempt directed toward Wesley or Alexander over the years, but admittedly, she is not overwhelmingly liked, & many of the above mentioned reasons are valid enough. For me personally, I really don't care for her episodes, because they are mostly weak episodes, & honestly? I never really thought Majel was much of an actor. Even her best, Half a Life, is championed more by David Ogden Stiers, & in one really powerful moment by Michelle Forbes, who are both excellent actors, that deliver some real weight in that episode, which is almost unheard of in any other Lwaxana episode.
The majority of the time we see her otherwise, it is one note... one incredibly, deliberately, irritatingly loooong note, & that carpet wears thin. There's a reason why Harry Mudd wasn't in numerous TOS episodes. Ostentatiousness is a dish best served in short measure. Overbearing characters can overstay their welcome, especially when your standard dynamic, as in TNG's case, was not very accommodating to that imho, & they already had another recurring character that offered it in far better proportions.