The general approach to Quantum Mechanics is that one first takes a classical system and then quantise to obtain a quantum mechanical system. This holds for QM itself, and QFT such as QED and QCD and also more esoteric theories such as string theory and LQG.
However, this strikes me as being a little backward. Surely, if quantum mechanics is a fundamental theory, and every indication suggests that it is, one ought to begin with a quantum mechanical system and then derive a classical world from it. That is we ought to have a Quantum Mechanics that is indigenously Quantum mechanical.
This seems to me a basic and fundamental question in physics, and I'm wondering what philosophically minded physicists, which of course, all good physicists should be (and have been in the past), have addressed this question in any substantial way (I do know of Causal Set Theory as one particular attempt) - or are they still busy obsessing (or spinning!) over 'so-called Quantum Supremacy?'