I would agree that it isn't a scientific hypothesis, but it's an important perspective, in a similar way that heliocentrism was an important perspective as opposed to geocentrism+epicycles.

For example, if we take Hossenfelder's argument and apply it to relativity, we have the argument that talking about a region of space is quite nonsensical because at any point in time an observer can only know that things in the past up to the distance light has travelled used to exist. But it is useful to model reality as a universe that can communicate at most at the speed of light.

Now, our current experimentation and exploitation of high-particle physics is still sufficiently immature, and the computations sufficiently inefficient that we can, and have to still rely on obvious collapse events. But if you eventually wanted to talk about, say, the two systems converging to the same state or diverging from the same state, then the MWI is a useful perspective, modeling the evolution of universe-space.