>>11766232MW is functionally useless and somewhat of a dead end in terms of research. If these many worlds exist then presumably it's not possible to traverse between or if it is there's not going to be a reliable method anywhere in the vast well of hocus-pocus that concerns the theory
Mathematically it doesn't really tell you anything you can use. Philosophically it's interesting, but also ultimately useless as it essentially implies that nearly anything can be true given that a world theoretically exists where it is true. It's kinda the polar opposite of solipsism but functionally it's just as much of a dead end. And a shit ton of popsci has been written about it which A: dilutes it's purchasing power as a theory among 'real' scientists (unfortunately, since this is possibly throwing the baby out with the bathwater, no matter how unlikely or mathematically futile) and B: attracts a lot of retards. All this together is kinda responsible for why MW isn't taken seriously (most of the time).
As for Copenhagen model, I'll let a physicsfag explain that one. I assume it's because it works as a good predictor of results but that is out of my field.