The movie is allegorical. Think Lost ,but done very poorly. The initial film adaption being called " Island of Lost Souls" really tips this off.
A Doctor, physician of the soul in a philosophical and religious sense, takes animals,who represent people dominated by their bestial nature, and makes them more human. New lost souls appear on the Island who upset the balance, and the beast-men who have never fully overcome their animal side take advantage and rebel destroying the doctor. The beats are lost after this point in Dr. Moreau, because it was handed off to people who didn't care.
However, if you put lost in Chronological order, which I won't do to avoid spoilers, it is essentially the same story, without the heavy handedness of making the people controlled by the baser part of their nature literal animals. You could essentially reverse engineer the beats from Lost to Dr. Moreau.