Many worlds requires postulates (Everett's word!) that are not a consequence of theory, in particular that the wavefunction is an objective property of a particle. This is very much in dispute, and is rejected by the ensemble interpretation, consistent histories, etc.

I don't agree that those interpretations are inferior to MWI. In particular those theories postulate that the world is essentially probabilistic, and so do not have MWI's trouble with predicting probabilities.