>It sounds all superior and mysterious to quote Feynman here,
It isn't about being superior, mysterious, or clever. The following "nobody understands" type of quips and thought experiments are different ways of saying our intuitions don't help us understand it :
- "God does not play dice with the universe.", Albert Einstein
- "Shut up and calculate", N. David Mermin
- "Schrödinger's cat" being both alive and dead
- various interpretations/analogies explaining quantum physics leading to absurdities or contradictions
Yes, humanity has harnessed quantum mechanics with mathematic frameworks and repeatable experiments to make useful things... but that's a different layer of "understanding" than the deeper levels in the above quotes.
"Nobody understands what gravity is." ... Wait, if nobody "understands" gravity, how did we send people to the moon?!?
Because those are different usages of the word "understand".
"Understand" means "Have a reasonable metaphor for."
Our monkey minds evolved to throw rocks at birds, and our metaphors are based on concepts like position, velocity, and temperature. We added first-level abstractions like energy and cause-and-effect, then built higher level abstractions on those basic concepts.
QM clearly doesn't work like that. It's probabilistic, possibly non-local, possibly subjective, possibly a holographic projection of some underlying reality that is nothing like this one, and its relationship with causality is slippery.
We have a mathematical UI for it, but that's not at all the same thing as understanding the machinery on the other side of the UI.