I don’t understand QBism well enough to really comment, but from the outside it seems like QM interpretations are taking the measurement problem increasingly seriously.
I like that the writer is up front in how all we really know right know is ‘shut up and calculate’ and wish that it had been taught with such honesty when I was taught it in school, rather than basically doing everything from the copenhagen interpretation and pretending that that isn’t fundamentally philosophically weird. The observer and measurement in the ‘shut up and calculate’ school is much more believable than in the copenhagen school where people (or at least things people do, like taking measurements and observing observables) are suddenly jarringly special for the first time in a physicist’s training.
Modern Copenhagen is basically an evolution from "shut up and calculate". It also doesn't given (human/conscious) observers any special role in QM - it is the measurement apparatus that has a special role instead.
Basically the initial approach was ontological: science is about what can be measured, when quantum properties are measured we need to apply the Born rule to predict outcomes, it makes no sense to discuss the scientific properties of what is by definition not measured, so shut up and calculate.
Later, the approach was more metaphysical: since our math doesn't work if we assume that particles have definite properties, we conclude that particles don't have definite properties; instead, when we measure their properties in a particular basis, the particles randomly acquire some definite property with a probability corresponding to the amplitude of the wave function.
Sure, that's probably a more precise way to say my complaint. The special role of taking a measurement/observing an observable. Unpacking what is and isn't measurement was what drove me nuts in undergrad and I never got an answer that satisfied me. We learned how to calculate the probabilities of each thing that would be measured, but not what counts as measurement.
I guess all I'm saying is that, in hindsight, I would have done so much better with a clearer delineation of 'this part over here is an interpretation question and isn't settled, but this other part over there is math that is settled empirically' rather than being taught 'here's an interpretation that's true and here's the math for it.'
Was the human conscious part ever a serious belief among actual physicists historically? I'm no physicist but it seemed obvious to me immediately that that could not possibly be the case.
Since Wigner was a Wise One (https://en.wikipedia.org/wiki/Wigner%27s_theorem) people took the idea seriously, but these days, most physicists will simply ask you to show them a comprehensible and reproducible experiment that demonstrates the requirement of a human observer and reject your belief based on the absence of data and occam's razor.
As the sibling comments are pointing out, yes, it actually was seriously considered for a while. Even today there are people like Roger Penrose who believe there is some link between consciousness and the measurement problem.
Even more, there are many interpretations of QM where the classical world is only an illusion of the observer essentially.
I like that the writer is up front in how all we really know right know is ‘shut up and calculate’ and wish that it had been taught with such honesty when I was taught it in school, rather than basically doing everything from the copenhagen interpretation and pretending that that isn’t fundamentally philosophically weird. The observer and measurement in the ‘shut up and calculate’ school is much more believable than in the copenhagen school where people (or at least things people do, like taking measurements and observing observables) are suddenly jarringly special for the first time in a physicist’s training.