—Paul Erdös
It may take another century, but I believe with absolute certainty that Einstein will be vindicated for thinking Quantum Mechanics was incomplete, rejecting the non-visualizable, non-intuitive, entirely algorithmic hoisting up of the mathematical machinery which Heisenberg, Schrödinger, Dirac, de Broglie et. al. built into quantum mechanics.
Einstein was on the far-most opposite end of the spectrum than all of them. Einstein was looking towards intuition to explain the physics and the experimental reality, while they were looking for mathematical models which seemed to fit the experimental data, while providing no understanding of what it all meant. Once Heisenberg & Schrödinger made a big break into QM, it's like all of physics jumped on it and forged ahead, damn whether anyone understands what is really happening.
Even Schrödinger himself, in his own first paper presenting his wave mechanics formulation, said there is no hope of visualizing nor understanding what Psi really represents. It's all just empty mathematical symbols, that when manipulated according to a particular set of rules, within a particular context, will give somewhat accurate predictions about some physical experiment. It really doesn't help at all the the entire QM apparatus is just plain ugly, inelegant and incapable of justifying itself. I'm not condemning it, nor any of the enormous geniuses who tossed their own contribution onto our great, immeasurable & eternal bonfire of accumulated human knowledge which we call science.
But if you read through a few grad-level books about QM, it's blindingly obvious that nobody really knows what's really going on. This is more of a consequence of our current gaps in mathematics, more than a failure of any individuals. Believe me, once someone discovers how to solve The Eigenvalue Problem in quadratic time, all of QM, as it is currently formulated, is going to go away and be replaced by a much simpler model. It'll be just as simplifying as centuries ago when we replaced Ptolemy's epicycles with Kepler's elliptic orbits. I bet even the probability concepts embedded in QM will be entirely thrown out(they were never anything but trouble anyways), and replaced by something even more fantastic & currently unimaginable.