The reality of Multiverse is undetermined and it is untestable. Unless someone discuss methods to test it, it's a waste of time because there is nothing to learn on our universe with it.

It would be a mistake to call back into question the existence of multiverse. And a mistake as big to claim it exist.

Until a method to test it is found, discussing this idea is a waste of time. However I would respect people searching and discussing methods to test it if they have pertinent things to say.