A qbit is not simultaneously 0 and 1, it is probably 0 or 1, and eventually - when measured - certainly 0 or 1. That's why 2n is wrong. A system of n qbits is not simultaneously in 2n states, it is probably in one of them.
Certainly, when measured, the result is 0 or 1, either/or, with 100% probability. I agree that far. But when we say that a qubit is 'simultaneously 0 and 1', that is a simplification. What we mean is that, prior to measurement, the qubit is best defined as a wave rather than a particle. The Schrödinger wave equation is the best description of what the qubit 'is'; really it makes no sense at that point to say that it is both 0 and 1, because 0 and 1 are classical end states. But we
can say that the qubit, because of its wave-like nature, can resolve to
either possibility. It has the potential to be
either a 0
or a 1. This phenomenon can be described as the qubit 'exploring all paths', but the fact remains that the power does scale 2^n, because
all possible classical states are potential outcomes upon measurement.
There's a lot of wishful thinking in quantum physics. It is believe based, and attracts all kind of believers. Something is fishy. It looks a lot like the geocentric solar system in Middle Ages. Circles upon circles, a very complex stuff, but never correct (except for a few isolated cases). So I would say, it is fundamentally wrong, and it is obvious.
Quantum mechanics describes how the universe behaves at an extremely small scale. It does not make sense in terms of our everyday, macroscopic view of the world. We have evolved to hunt food, search for shelter, escape predators. This is how our brains are built. Our understanding of what constitutes reality is heavily influenced by our sensory apparatus. A rainbow, for example, only appears as does because of the way our eyes work; other eyes would see it differently, and the mathematical description would see it perfectly.
Any attempt to explain QM in everyday human terms will fail; this is why no human really understands what the quantum world 'is'. But we have mathematics that describes it. And we have devices built on that underlying mathematics, and these devices function correctly according to the laws of QM. We cannot say this is wishful thinking, rather it is verifiable, reproducible experimental evidence. It is fact. Modern computers are built on quantum mechanics. It is impossible to describe semiconductor-based electronics without quantum mechanics.