You appear to be somewhat mistaken. Copenhagen interpretation does not postulate any specific explanation or mechanism for wave-function collapse, merely that "upon measurement, the wave-function collapses into an eigenstate of the observable being measured". This, of course, is a physically verified phenomenon. Now Copenhagen purposefully leaves the precise meaning of "measurement" undefined, since in my view there is no convincing empirical evidence that supports a specific mechanism for this phenomenon. Other interpretations posit mechanisms (decoherence (doesn't fully account), von Neumann "consiousness" (not empirical), etc.) for this collapse.
My biggest complaint about many-worlds interpretation is how it is in its essence a non-scientific theory, as it makes assertions about an unobservable reality. It postulates other parallel realities that by definition do not communicate. Again, this makes it intrinsically a non-scientific theory.
>Can you tell me under what circumstances a system of particles will evolve unitarily or not?
Everywhere except on measurement, in which the state collapses.
>How about in a delayed choice quantum eraser experiment?
I'm not familiar with this experiment.
>If you tell me "you're not allowed to ask those questions"
By all means, ask as many questions as you want. That's after all the essence of scientific endeavour. But it's not very nice to misrepresent other positions, nor is it to claim everyone else is deluded (without strong evidence on your side at least).
>Bell's theorem should have sent a shockwave through the community which forced everyone to reevaluate fundamental assumptions and self-correct wrong ideas.
Bell's inequalities force no re-evaluation. They simply prove that the search for a local hidden-variable theory is impossible. It certainly raised important ideas for research, but it does not do anything to discredit established QM.
>The claim that "the meaning of QM is outside the scope of science" is exemplary, I think, of that attitude.
If a physical argument can be made about this problem, then it's in the scope of physics. Otherwise, it is not. As simple as that.