One of Einstein's objections ( and the most pertinent one for this thread) to QM is that many of its advocates are logical positivists. Einstein did not just give equations that could be experimentally verified he provided a description ( in this sense Einstein was metaphysical , see above post). For example gravity is curved space-time.* The interesting thing is that in academic philosophy logical positivism is considered the only belief system that self destructed. It is based on the rejection of metaphysics ( an over all description of reality) and yet its basic premise is metaphysical!
* Einstein's genius was to approach a problem by visualizing a thought experiment. For example Relativity is the result of his visualizing and speculating about what the universe would look like if one rode a photon. Of course Einstein knew that that was impossible and to make that objection is nonsense.