If it was fiction, this movie would be camp grotesquery along the lines of "Whatever Happened To Baby Jane?" or "Sunset Boulevard", and perhaps very good indeed. But since it's a documentary, it's a "cult classic", meaning that most viewers won't enjoy it much, unless they're the sort of kidult who deliberately watches bad films ironically.
This glimpse into the extremely limited lives of two half-mad recluses who happen to be the aunt and cousin of one of the richest and most famous women in the world, yet deliberately live in disgusting squalor in a fast-disintegrating 28-room beachfront mansion, exerts a kind of horrible fascination, and might be of great interest to psychiatrists, but in the end, what's the point? The most dramatic event in the story - the health department forcibly cleaning the ground floor with fire-hoses - happened a year before the camera crew arrived, and everything else of real interest occurred even longer ago, so what we get is two extremely self-centered poor little old rich girls locked into a very unhealthy relationship talking, shouting and singing at each other almost constantly, mostly at the same time.
By the way, the squalor really is disgusting. Their eight scrawny flea-ridden cats are neither allowed out of the house nor provided with litter trays, but that's OK because Edith Senior likes the smell. Little Edie doesn't, and repeatedly says she wants to get out of this place, where she's apparently been trapped for a decade. But come on lady, you were already middle-aged when you let your loopy miser of a mother persuade you to live with her as a social outcast in the world's biggest cat lavatory! How did these women who once partied with the world's élite, and have relatives who still do, get this way? And why have the rest of their mega-rich family given up on them so completely for so long? A story like this needs lots of background, but we get none at all except what the two women provide, and they almost always contradict each other, usually while the other is still talking.
I suppose you could view this as the bittersweet tale of a symbiotic relationship between an aging control-freak and the only person she can still control, her spoilt daughter who at the age of 56 behaves like an adolescent because she never learned how to take responsibility for anything including herself. But for that to really work, you'd need dialogue by somebody like Samuel Beckett or Harold Pinter, instead of letting these not particularly bright and very loud crazy cat-ladies improvise for an hour and a half. Well before the end I felt they'd made their own bed and thoroughly deserved to lie in it, feline by-products and all.