Unpopular opinion I think, but I still believe the physics world was wrong to chase the Copenhagen interpretation.
The math does indeed work, and many experiments and practical uses seem to show that there is something to quantum broadly. But to throw determinism out the window and believe that quantum is fundamentally probabilistic, and that one can never really run scientific experiments because observing state collapses superposition, has always seemed asinine to me.
I could be completely wrong, but it's always seemed obvious to me that the need for probabilities in quantum is a clear indicator that something is missing in the theory. I'm never surprised when a person can't understand quantum as its described today.
It's completely counterintuitive, but that's how it works experimentally. For example:
Measure the spin of electrons in direction X (that's done with a weirdly shaped magnet). You'll get either +1 or -1 in a conveniently chosen unit system. That's already weird, you'll never measure +0.5 for example. Keep only the +1 electrons. You can measure them again and again, you'll always get +1 in the X direction.
Now measure those electrons in the Y direction, you'll also get either +1 or -1.
But now, if you measure in the X direction again, you'll get +1 or -1 with 50% probability; although before measuring in the Y direction, these electrons always had spin +1 in the X direction.
Oh I get that experiments prove out. What has always been unintuitive to me to the point of seeming wrong is that said spin is random and lives in a probability cloud that is probabilistic only until we observe it.
The math works and the experiments work, but it feels like a broken clock situation. It happens to correlate well, but the understanding and models are missing something in the actual underlying physics that, if understood, would throw the whole randomness part out the window.
> [the] spin is random and lives in a probability cloud that is probabilistic only until we observe it.
My mental model of it is kinda reversed. The maths assign a specific, deterministic state to each electron between each measurement. However, the "left" state is equal to "(up + down) / sqrt(2)". It then follows that when we measure an electron that is in the "left" state along the vertical direction, we get 50% up and 50% down: the probabilistic behavior happens when measuring, which "forces" an electron that was in the "left" state to become either "up" or "down".
I agree though that it would be less frustrating if there was some property of the electrons that would allow to predict in which state it'll collapse.
It has been shown that you can keep determinism (Bohm etc), but what follows is not necessary something you'll find more intuitive or cleaner or more logical.
I haven't been sold by pilot-wave theory, adding hidden variables to attempt to get rid of randomness feels like a cheat rather that a realistic view of how reality would work.
Unrelated, but I also wish scientists properly used the term "theory".