I'm just an old industrial physicist, but as I understand it, quantum gravity has yielded no testable predictions so far, and neither have multiple-worlds theories.

I never said anything about quantum gravity. String theory is also trying to bridge things. But many worlds is pointing to a gap in the math and claiming god. All I’m saying is we don’t have any model or math and many worlds is the more fantastical explanation.

It's simple and elegant if you like it, overcomplicated if you don't.

Many worlds is a philosophical interpretation akin to god. It doesn’t add anything to our understanding and instead invokes some kind of supernatural untestable phenomenon.

The many worlds are a consequence, not a postulate. It is the Copenhagen interpretation that postulates that all branches but one disappear at measurement.

Both of them are interpretations. We have no reason to believe one over the other.