They're different kinds of complexity, though. QM isn't too bad. The basic ideas are alien but straightforward enough. It's hard to extend small examples to la

They're different kinds of complexity, though. QM isn't too bad. The basic ideas are alien but straightforward enough. It's hard to extend small examples to larger systems, though, and that plus the innate weirdness really messes with your intuition. BJTs are complicated devices built from multiple simple-enough effects all happening at the same time. Each piece isn't too bad, but you've got to track them all and combine them into an overall function. QFT (quantum field theory, such as QED) is basically all the bad parts of both of those: the basics aren't too bad, but it's difficult to scale, there's a lot going on, and it's hard to develop intuition. QCD then makes the basic calculations intractable, which is why it's still poorly understood to this day (in my opinion). So, yeah, in conclusion, complexity is complex? Not so profound, I guess.