[uoaei]

Many Worlds Interpretation suffers from a more catastrophic and incredibly strong assumption, namely that all of the possible universes are real. That seems far-fetched on its face, though could still in principle be possible I suppose.

Quantum Bayesianism ("QBism") softens the strong claims about reality to merely those about subjectivity, i.e., you cannot know that which cannot be represented by the configuration space of your lightcone. In other words, possible futures are possible only when there is an unbroken causal chain from your present to that future, and you will be ignorant of anything outside of your lightcone. It stresses the uncertainty inherent in a singular perspective of spacetime's unfolding, rather than an uncertainty of some mythical "wavefunction collapse mechanism".

[hilbert42]

Yeah, right. Philosophy was once part of my curriculum and some propositions/arguments in favor of MW would seem more apt therein. Phil. also had a strong formal logic section to it so I consider your other QBism points well put.