Rumors about The Island of Dr. Moreau’s suckage have been greatly exaggerated. The real problem with this film isn't so much that it's bad, but that it's not nearly as good as it should be considering the actors involved; on the other hand, it is precisely these individuals (and none more than Marlon Brando) who barely manage to save, perhaps even in spite of themselves, this particular island from sinking to the bottom of the sea.
Brando invariably was the best thing about his good films, and the only good thing about the bad ones — this one is no exception; indeed, his portrayal of the titular scientist is one of the ways this version is superior to that of 1977. For all its flaws, I would go so far as to say that this is the best possible film of The Island of Dr. Moreau.
Whether by design or accident, Brando turns the weirdness all the way up to 11 — at one point, for example, wearing a “caloric converter” into which Fairuza Balk pours chunks of ice —, which is exactly what the role requires: the good doctor can never be anything other than the maddest of mad scientists.
When David Thewlis asks him whether “has it ever occurred to you that you might have totally lost my mind? I mean, this is just satanic”, the implicit, tacit answer is no — of course such a thing has never occurred to him, because lunacy has so absolutely taken over him that sanity and insanity are now one and the same thing. Brando’s Moreau is essentially a Kurtz whom "the horror" is no longer capable of horrifying.
By the way, the issues Francis Ford Coppola faced while filming Apocalypse Now — recounted in the documentary Hearts of Darkness —, including how to get the most out of Brando, make Moreau '96’s vaunted troublesome shooting feel like a picnic in comparison. Coppola somehow managed to create one of the greatest films in history — but then he is Coppola one of the greatest director/screenwriters, something John Frankenheimer will never be accused.
All things considered, it's possible that Moreau '96 would have done much better with lesser-known and even less talented actors; this is a visual story, after all, and the key is to reflect on screen the images that H.G. Wells brought to the page.
The most important thing here is the spectacle, and this is why Brando rises above the material: because he does not have or does not know the fear of making a spectacle of himself, equal to or even more grotesque than Dr. Moreau’s creations.