So you're an MWI proponent, then? If it's "obviously true" to you that everything, including measuring devices and ourselves, always evolves in time exactly according to the Schrodinger equation, no exceptions, then the MWI is your only option as an interpretation.

The fact that many people do not think the MWI is a viable interpretation is why interpretations like Copenhagen, which do not rest on the belief that the Schrodinger equation has to be literally true, everywhere, all the time, continue to exist.

But once you start trying to really tease apart the potentially metaphysical question of "what's actually happening?" (a question many people believe is just not within the realm of falsifiability/science), traditional collapse theories have a bunch of trouble setting up clear lines of what macroscopic is, how collapse actually occurs, etc. that do not seem to have easy resolutions, especially as we can create bigger and bigger quantum systems.

All of this is true. But none of it makes it "obvious" that the Schrodinger equation must always be exactly correct and that one should be "dumbfounded" (your word) that any interpretation (like Copenhagen) that says otherwise has any proponents at all. Yes, "collapse" is an obvious open question that hasn't been resolved. But the belief that some way of resolving it will eventually be found that doesn't require accepting the MWI is a perfectly reasonable belief to hold, and an interpretation like Copenhagen is a perfectly reasonable interpretation for people to use in the interim while we search for such a resolution.